Contents Page 4 Introduction 5-6 Chapter 1; Large common liverworts
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| 12. In Vitro
Ever since Louis Pasteur's experiments in the early 19th century, it has been understood that bacteria exist almost everywhere, and that the only way to keep food fresh, or to culture most microscopic organisms, is to exclude unwanted bacteria. Growing sterile cultures on a nutrient medium, in a test tube or a Petri dish, is an essential in many biological projects, and techniques for doing it have long been familiar, to scientists, at least. In more recent years these techniques have been extended to higher plants. Orchid seeds were first germinated on a sterile nutrient medium in the 1920s, and the method is now widely used. Scientists, some commercial growers, and even a few enterprising amateurs, are making increasing use of similar methods, to make meristem cultures of other hard-to-propagate plants and seedlings. Since many bryologists are trained biologists with access to laboratory facilities, it is natural that sterile cultures have been used for growing mosses. They have been attempted for many mosses that do not like life in a test tube, and the failures may have helped to reinforce the mistaken idea that mosses cannot be grown without sophisticated methods and equipment. Nevertheless, for certain groups of mosses, sterile cultures are well worthwhile. Small acrocarps of disturbed ground, fields and garden beds, are often difficult to identify. Another very difficult group is in the genus Bryum. Many years ago, Dr. Harold Whitehouse of Cambridge became interested in these, and cultured them in glass test tubes, on an agar solution containing common plant nutrients. Since they were growing in a transparent medium, the rhizoids, which are normally hidden in soil, could easily be seen. On the rhizoids of many species, tiny tubers formed in culture. They could be far more easily seen and studied than the tubers on wild plants, which are invariably mixed up with soil, and often with the tubers of other species growing alongside them. It soon became obvious from these cultures that even in Britain, there were several little-known or even undescribed species, some of them quite common, which could at last be readily identified by looking at the shape, size, or colour of these tubers. The result has been a major contribution to our knowledge of these plants. Dr. Whitehouse also kept pure cultures of many very small or short-lived mosses for many years, in a way which would have been impossible or very difficult, in flower pots or unsterilized cultures. The most difficult task, outside a laboratory, would be to make a suitable nutrient solution, though such solutions can be bought commercially. However, for some years Fisons have been marketing a nutrient gel, "Cleargel" for use in rooting cuttings, which is available in some shops and garden centres. It can be used to grow at least some mosses, without the need to mix chemicals or go to specialised suppliers.
Like mounted cultures, test tube cultures are worth preparing in batches before they are actually needed. I have started by soaking test tubes in a 10% solution of "Happy Shopper" domestic bleach, then rinsing them in hot tapwater, which, like boiled water, is unlikely to contain live algae or spores. A little Cleargel can be scooped on a very small spoon, screwdriver or similar implement, which has also been sterilized with bleach, and put at the bottom of the tube. Unlike agar, this gel cannot be easily melted and run into the bottom of the tube, so this is the messiest part of the preparation. Lids, if any, can be similarly bleached, or the tubes sealed with bits of clingfilm, or with polythene and rubber bands. They may still smell of bleach, so it is probably a good idea to set them aside for a few days before use, so that any remaining traces evaporate or are broken down. The whole operation should be carried out indoors, in a place reasonably free from draughts and dust. Once opened, the original pot of Cleargel must of course be kept completely clean and covered. Sterilizing the moss takes some preparation and practice, and it is worth dealing with a fair-sized batch of plants on one occasion. It is most convenient to set out a strong lamp, tweezers, a pipette, a good lens, some fresh kitchen tissues or porous toilet paper, and two or three saucers of clean water, together with an empty saucer - preferably a white one, on which tiny fragments of moss can be easily seen. To sterilize, only a few drops of diluted bleach are needed. I have used about a 10% solution of Happy Shopper bleach, but different brands may be best used at different concentrations. The intention is to kill any algae or spores on the plant surface, but not the plant itself. With tweezers, take a single clean shoot, or a single leaf or stem fragment, or perhaps two or three small shoots, but no more. If there is any soil on them, rinse it off in water. Place them on the empty saucer, add a drop of the dilute bleach with a pipette, or in any other convenient way, enough to completely cover them, shake the fragments around in it with the tips of the tweezers, and watch them through a lens. After a time, from a few seconds to a few minutes, the edges or tips of the leaves will become bleached, the green colour disappearing. At this point, before the whole plant has lost its colour and been killed, remove it with tweezers, rinse it in clean water, and blot off any traces of water and bleach by putting it on the tissue. Repeat the rinsing and blotting process two or three times, to completely wash it, then put it on the Cleargel in the test tube with the tweezers, and put on the lid. If the specimen becomes bleached in less than about 10 seconds, you will probably not rinse off all traces of bleach quickly enough to prevent the plant from being killed completely. A more dilute solution of bleach will be needed. If the rinsing and blotting is not thorough enough, it will also die. However, so long as even only one or two cells survive, it will regenerate. With most cultures, it will soon be obvious whether the plant has started to grow. It should produce new protonema within a week. If not, and if it is no longer green, you have overdone the bleaching and killed it, and must start again. Too weak a mixture will not kill algae, especially if there is the least trace of soil in the culture. They will form green blobs or a green stain, and are likely to poison the moss in the culture within a few months, though it will usually outgrow them at first. The results, in my hands at least, were much less attractive to look at than flower pot cultures. Some mosses of acid soils did not grow in such cultures, perhaps because I used alkaline tapwater for rinsing and sterilizing. Nor did most hepatics. I concentrated on acrocarps, especially Bryums, Tortulas and their relatives, and on ephemeral mosses, (Phascum etc.). Within these groups, the initial success rate was fairly high, about 80%, though most did not grow in hot summer weather. These were all plants which produce protonema fairly freely. Many also make tubers. Some, in test tubes, are reluctant to make any normal leafy shoots at all. However even the slowest of epiphytes, such as Orthotrichum, can make quite large amounts of protonemal growth, in a far shorter time than under more "natural" conditions. Labelling test tube cultures can be tricky. Adhesive paper tags fade or decay, or are nibbled by insects. Chinagraph pencils can write directly on glass, but are usually too blunt, and may wear or rub off. Since the object was to try out test-tubes as a means of long-term storage, I made about 100 such cultures in 1990, which were left for 4 years untouched, in a shaded corner of the greenhouse. About half died in this time. Algal contamination was occasional, but more likely causes of death were too deep shade, high temperatures, and perhaps unsuitability of the growth medium. Unfortunately, the trial was spoilt by the failure of the different labelling systems I tried. Only the labels for groups of cultures survived. The clearest conclusion was that many died, but that almost all the Bryums (though I did not always know which ones) were viable after 4 years, regenerating from protonema when put on mounted loam. It seems fairly easy to move plants between sterile and conventional cultures. Almost all my sterile cultures were started from cultivated material. Conversely, sterile cultures in their blob of Cleargel can be simply pulled out of the test tube, and planted like normal material of the same species. There is one compelling reason for growing mosses in test tubes. It has nothing to do with the advantages to botanists who may wish to do serious taxonomic work on difficult species, as already mentioned. It has more to do with the personal problems of hard-pressed and semi-bankrupt students - especially botany students. Test tubes are small. Ten will fit in a jacket pocket, a hundred in a bicycle saddlebag, and five hundred in a rucksack. A university student who is turned out of his hall of residence on the last day of term, to make room for money-spinning conferences - as they usually are these days - can take a reasonable proportion of the British moss flora home with him, growing in test tubes. Then he can leave them in a shady place under his parents' rosebushes during the long vacations, while he sweats to pay off his student loan. This is not a frivolous point. A large proportion of the people who are interested in mosses first became aware of them while studying botany in 6th forms or at universities - at precisely that stage in their lives when they were most footloose, most hard-up, and least able to maintain a garden, a greenhouse, or any other conventional collection of living plants. Their personal circumstances conspired to reinforce the message from past generations of academics - that real botanists do not grow plants, but squash them flat, dry them, and put them in paper packets with a Latin name on. Far from being difficult to grow, mosses are in some ways uniquely convenient. Even the most rootless student, or the inhabitant of the most claustrophobic urban flat or maisonette, can hope to build up an interesting and worthwhile collection of these tiny plants. 13. Mountain Mosses There is a great contrast between the inhabited parts of Britain and the barren windswept uplands which cover much of the country. Though most of these uplands are rather featureless, and botanically poor, the cool wet climate encourages the luxuriant growth of mosses. In steep rocky and mountainous country, as in the Lake District, there are many more habitats, and many more species, enough to overwhelm most beginners. Good advice to beginners is, not to start in such rich areas, and more especially, not to try collecting, identifying or growing large numbers of mosses from the mountains, until you have some experience with at least a few lowland species. After gaining that experience, it is far easier to appreciate the different mountain habitats and their distinctive flora, even if most of the species are still unfamiliar. No real plant lover ever tackles a mountain in the mindless manner of the typical tourist. The unremitting application of alternate feet to an eroded path, the straight route to some blasted summit and down again - this is a waste of botanical time. Most of the best plants will be found well below the summits - even near sea level, in the wettest parts of Wales and Scotland. The botanist will often follow a stream, preferably into steep ravines and gorges whose banks are dripping with wet cushions of vegetation, and where even the sheep cannot reach the flowers and nibble them. In a place like this, an experienced bryologist can record a hundred kinds of moss before lunch. It would be unreasonable to try to describe even a proportion of them. Steep western oakwoods, full of rocks and boulders, are often covered in a deep layer of large mosses, and are an easier place to start looking. The largest and commonest are often Rhytidiadelphus loreus, like R. squarrosus but larger. Dicranum majus, Hylocomium splendens and Isothecium myosuroides, described earlier. Of the 40 or more species common in such woods, most are less obvious. It is on the steepest boulders and rock faces that the greatest variety of smaller ones will usually be found. There are certain also to be leafy liverworts. The wetter the climate, the larger and more varied they become. Plagiochila asplenioides and the larger P. porelloides are likely. They occur also in lowland Britain, but there are other smaller western Plagiochilas which have more strongly toothed leaves. P. spinulosa is the commonest. Others are rarer and mostly smaller still. Lepidozia reptans may grow more luxuriantly than in the lowlands. L. pinnata, which makes large pale cushions, is locally common in the far West. In this genus are other smaller, less common species. Bazzania trilobata, is even more striking. Its arched and flattened shoots can be 3-4 inches tall, with large three-pronged leaves. Like some other large leafy hepatics, it makes specialised stems, pale, almost leafless, and pointing downwards, called flagellae. They are often covered with rhizoids, and in their function resemble the roots of flowering plants. Growing as they do on steep slopes, all these need strong drainage. In culture, wet soil or waterlogging will quickly kill most of them. They can be grown on Sphagnum peat or acid fibre, in clay pots. According to my experience since 1990, they often make cleaner and more reliable growth on mounted peat. They can tolerate moderate or deep shade, and must be protected from all direct sunshine. Above all, they only grow well in high humidity, and are almost certain to need an enclosed frame or a covering of polythene, at least in summer, to grow well. On the other hand, so long as they are well sheltered and humid, they can be left to slowly dry out for long periods, even in summer. Plagiochilas are the most tolerant, and can be left for weeks, unwatered and unattended, if they are well shaded and humid. On wet bare soil, by trickles of water and riversides, and on boulders in and by streams, there is a different selection of species. Large pale blue-green tufts are probably Philinotis fontana. On shaded wet soil in boggy woods, on banks or stream sides, Hookeria lucens is frequent. Its flattened stems and large round leaves with glistening cells are quite distinctive. It looks quite unlike any other British moss, resembling, rather a large liverwort. Dark straggling mosses with wiry stems and blunt leaves, on boulders in or by water, are usually Racomitrium aciculare or R. aquaticum. On such boulders are usually mats of pleurocarps. A creeping moss which resembles Brachythecium rutabulum is probably B. rivulare. It can be distinguished by the patch of inflated transparent cells at the corner of the leaf, where it joins the stem. There will also be many hepatics, especially Scapanias, with their complex folded leaves. On damp shaded soil, Nardia scalaris and Diplophyllum albicans are very common, together with several other Nardias or related plants with round leaves, which can be hard to name. Though all these may grow apparently side-by-side, they have widely differing needs in culture. The hepatics of wet shaded soil are relatively easy to keep. They need shaded acid or neutral soil, and constant moisture. A plastic flower pot in a tray of water on the damp cool greenhouse floor, with fairly frequent spraying and a little standing water, suits them well. So does a small frame or propagator in a shady place outdoors, or by a sunless window. Brachytheciums and other pleurocarps do not like too much shade, or wet warm conditions, so unless they can be kept quite cool, it is better to keep them rather dry, and grow them like the garden Brachytheciums mentioned earlier. Dicranella squarrosa makes big pale tufts by streams, with recurved (squarrose) leaves. It is unlikely to survive for long in a warm greenhouse. With artificial light, I have kept it through a hot summer on the floor, cooled a few degrees by a nearby refrigerator, and on wet soil in a refrigerator. Paradoxically it has also survived, in a very stunted form, on rather dry mounted soil, in the same conditions as other small Dicranellas. In contrast, Philonotis species grow well on waterlogged soil in a good light, even in fairly hot sunny conditions, though they need replanting each year. The Scapanias, with erect stems and folded leaves, are very striking, especially S. irrigua which makes large brightly- coloured purple, red or green tufts, in weakly flowing water. These are probably the most difficult waterside plants to keep. I have found them very unpredictable in their response to cultivation, and cannot offer reliable advice on growing Scapanias of wet habitats. Those of drier habitats are best mounted, shaded, and in high humidity. It must be remembered that even mosses and hepatics which grow side by side in the same habitat may need very different cultural treatment. Exposed boulders on mountains have relatively few species, all of necessity adapted to harsh conditions, and frequently dried out by sunshine and fierce winds. Hypnum cupressiforme is likely, and where a little humus has collected, one or two common species of Polytrichum and Campylopus. Of more interest to a visitor from the lowlands will be Racomitriums and Andraeas. Racomitrium is a remarkable genus. Two riverside species have been mentioned. There are several others. The commonest and most striking is R. lanuginosum, which makes large hoary creeping carpets. At high altitudes, and on barren screes and summits, it is often the most abundant plant, covering large areas. Most of the Racomitriums of dry rocks (though not those of wet rocks) are common also on acid walls, as of slate in mountain regions. They are much rarer in the drier lowlands, on thatch, heathland, old cinders, and acid tombstones. Equally common on mountain boulders, even on high summits, is R. heterostichum, a densely tufted plant like a Grimmia. It varies from olive-green cushions, which can be quite large, to tiny black tufts (now considered a separate species, R. affine), but usually with a small hairpoint, visible under a lens. A brighter yellow-green plant with spreading twisted leaves and no hairpoints, creeping closely pressed against the rock, will be R canescens s.l.. There may be creeping patches of the dark purple hepatic, Frullania tamarisci. Among these, and among the many colourful mountain lichens, will be small tufts of other mosses, so black that even when moistened and examined under a lens, they appear lifeless. They are Andreaeas, probably A. rothii. Growing these extraordinary plants will never be a hobby with a mass following. The first thing to understand is that they are adapted to a nutrient supply which, by ordinary gardeners' standards, is fantastically low. They get all the nourishment they need from hard acid rock and clean mountain rain. The second thing to understand is that they grow strongly, even on the highest and coldest mountains, where summer weather is hardly warmer than December in Berkshire, and certainly wetter and windier. The third is that they can stand drought of almost unlimited severity, and yet spring to life within seconds when moistened. When a dry tuft of Racomitrium lanuginosum is sprayed, the change from lifeless grey to bright hoary green is almost too fast for the eye to follow. I can only suggest three fairly distinct ways to grow Racomitriums; Pieces of broken roof slate or hard granite can be wedged into the top of a clay pot to give a strongly drained permanent surface of hard acid rock. Slate is most convenient, since the parallel strips leave many gaps into which the moss can be pressed. Such cultures may be unsuccessful in a greenhouse, since nutrients collect in the pot, or in the gaps between the pieces of slate. Other mosses such as Bryum bicolor soon appear, and eventually outgrow the Racomitrium. I had one, in which R. canescens grew on acid sand in moderate shade, but needed weeding to remove Ceratodon purpureus. However, in the open, these nutrients are leached away by rain, and the weed mosses discouraged. The oldest such culture I have, on pieces of hard acid sandstone, wedged into a clay pot, was made in 1989. It became covered in young shoots of R. heterostichum, which colonised new sandstone fragments, despite being on an exposed sunny south-facing veranda, outdoors. Most of my Racomitrium cultures were on mounted granite. Some were treated like epiphytes, but some of the streamside Racomitriums, being more shade-tolerant, were on shadier lower shelves, and kept moist for a larger part of the year, perhaps even through the summer. Third, some were in constant high humidity, quite shaded on a cool lower shelf, on well-drained or mounted peat, mostly as chance associates among delicate hepatics. Racomitrium is one of the most widespread and abundant genera of high arctic-alpine mosses. Any cultural method that works for Racomitrium is likely to work for many other mosses of exposed acid rock. They include the very attractive Hedwigia stellata, (not at all shade-tolerant) and many of the British species of Grimmia. I have found Grimmias more tolerant of hot sunshine, and of shade and mistreatment. Most can be grown on mounted rock cultures, though they are slow, taking at least 3-4 years to make good tufts, which can then persist for 10 years or more. So far as I know, virtually none of these mosses of rocks have been kept alive elsewhere in cultivation until recent years - if at all. Among the mosses on more sheltered rocks may be a few hepatics. Species of Lophozia are quite common, especially on thin humus, rock and turf ledges, or on somewhat sheltered boulders. They are best treated like the common lowland L. ventricosa, fairly well shaded, on strongly drained or mounted peat. Higher on mountains, especially in the far West, and above 1500 feet, other small hepatics grow on cliffs or boulders, with minute tight-packed leaves. Gymnomitrion crenulatum makes small coppery-red or black patches. On bouldersides or cliffs, G. obtusum, with rounded leaf lobes, and G. concinnatum, with more pointed lobes, make silvery-green, grey or ochre tufts. They are often in places blasted clear of snow by winter blizzards, whose scouring action destroys most other plants. More abundant than these, making large rubbery mats of tiny silvery white stems in or by icy cold mountain streams, is Anthelia julacea. Unlike Racomitriums, these cannot survive drought or hot sunshine. Therefore they cannot be left dry and dormant in hot summer weather. Nor can they tolerate high temperatures. At best, in the coolest corner of a lightly shaded garden or greenhouse, they will languish for a year or so before dying, or getting overgrown by other mosses. The same may be said of Marsupellas, a large and mostly high alpine genus. Only one species is really common and abundant. Marsupella emarginata has erect shoots and shallowly bilobed leaves. It makes tufts, sometimes of a deep reddish-brown colour, common on wet rocks by cold mountain streams. These must be among the most difficult of all bryophytes to grow. Only if you can keep Marsupella emarginata is it worth trying to grow any of the others. It is probably a waste of time to even think of it without some experience, and a well-organised infrastructure, a supply of pure water, and so on. Yet among cactus and succulent experts, I have never yet met anyone who despises a plant because it is small, unusual, or difficult to grow - quite the opposite. The new, the obscure and unusual, the plant which nobody else can keep alive, this is the challenge which a real enthusiast seeks out and cherishes. In early days, my rather forlorn strategy was to split cultures of these difficult plants, and to try contrasted conditions, a well-lit but hot hotter dry top shelf, or a cooler but shaded position on the greenhouse floor. In general they survived longer on the well-lit shelves, despite the higher temperatures, but death was inevitable for many of them. In early 1990 I brought an electricity supply into the greenhouse in Reading, and installed a Growlux light and an old refrigerator. The results confirmed my belief that these plants need strong light and low temperatures, or better, a combination of the two. The refrigerator door was taken off and replaced by a transparent plastic door, held shut by the magnetic strips used in the "Magnelite" double-glazing system. The inside was poorly lit, but offered a variety of summer night time temperatures between 2-8C., and daytime summer maxima in late afternoon between 10-20C, depending on the weather.
Just as British farmers have woken up to the fact that over much of the Southeast, irrigation can improve crop yields, so may enterprising plant growers yet discover that many familiar plants, especially alpines, can be grown better if given lower night-time temperatures in summer than a normal greenhouse can provide. Spitzbergen, for instance, has a surprisingly diverse flowering plant flora, with many endemic species, all adapted to a growing season of at most 3 months, and to a summer temperature averaging 5C. The alpine house at Kew Gardens has a display of high alpines and Arctic plants on a refrigerated bench. It is the soil and roots, rather than the air above the plants, which are cooled. Some of these plants spend their winters at -6c in a freezer. In late 1994, I picked out about 30 mosses and liverworts in gatherings from northeast Greenland (Peary Land) made by a friend that summer. Most were simply put among their British relatives, rather than in the refrigerator, some mosses even on the hot exposed top shelves, and few were immediately harmed by this unlikely treatment. Some soil cultures were kept at, or just above, freezing by the refrigerator icebox. Most of the hepatics (some also occur as Scottish high alpine species) were on mounted cultures, in high humidity. Though unrefrigerated, most survived hot weather in summer 1995. In the British Isles alone, there are dozens of high alpine hepatics and many alpine mosses (especially Andreaeas) which neither I, nor anyone else, has yet kept healthy. Those I have grown often behave in surprising ways. Virtually nothing is known about the growth rates or ecology of many of them. Any reader who rises to this challenge and keeps them for any length of time will certainly add to the sum of scientific knowledge. Given a cool greenhouse and a less hostile local climate, even refrigeration may be less necessary than well-drained mounted culture conditions. I commend these arctic- alpine plants to anyone who is willing to experiment, at least with the common ones. Paradoxically, a refrigerator is also a promising heat source. The motor is a heat pump, and a heat pump can deliver more heat than an electric fire or heater with the same power consumption. The cool air sinks, and the warm air from the radiator on the back moves upwards. For a gardener who has only a few plants to keep warm in winter, a frame put on top of a refrigerator, to catch the warm air from the radiator could make better sense than a conventional electric heater. Refrigerators, it is true, are bulky, mainly because of the insulation in the case. Yet, if some pundits are right, we will all be conserving energy by using heat pumps, in fifty years time. On a mountain, it is usually a good idea to look at the north side. Steep north-facing turf slopes often have a rich hepatic flora. This is especially true of those which get little direct sunshine, or which are shaded by tall bilberry or heather. In such places there is a specialised flora of strange and sometimes spectacular hepatics with a strongly western distribution. Even the commonest are confined, in Wales and the Lake District , to the wettest and most mountainous parts. On the higher or wetter mountains of west Scotland and western Ireland there are several more. They often grow best at about 2000 feet above sea level, soaked by mist and drizzle for 200 days in the year, or more. Many of them are absent from Europe, or found in only a few sites outside this country. Strangely enough, their close relatives are often found in the wet forests of high tropical mountains. They clung on here through the Ice Ages, on bleak hills in the far West.
In the past, they generally persisted here for a long time if shaded and well drained. Poor drainage or sunshine would quickly kill them. They need high humidity to grow at all, yet in an enclosed frame or container, growth can become etiolated and unnatural, especially if too deeply shaded. Most can flourish on mounted peat (and some on peat in clay pots) well-shaded, and covered with polythene to maintain high humidity throughout the year. If kept moist and humid, they continue to grow better than might be expected in warm summer weather. Sometimes they can also be grow in wet peat, especially Herbertas, but kept thus, they often get mucky and overgrown. Most of our mountain country is composed of hard acid rocks. Lime-rich and nutrient-rich rocks soils are rare at high altitudes. Where they occur, they support a distinctive flora which is also rare. Beginners should not seek out such places, since the moss flora of some of them may have suffered from the past activity of collectors. Yet my impression, strangely enough, is that most of these rarities are easier to grow than the more widespread plants of more barren acid rocks and soil. It is the barrenness, the low level of nutrients in most mountain habitats, which is hard to reproduce in culture, even more than the climate However, one common mountain habitat does offer more nutrients than open moorland or bare rock. In damp or overhanging rock clefts, especially where there is some seepage of water, or where soil has collected, several distinctive mosses often grow. There may be Pohlias, especially Pohlia cruda, which has young shoots of an astonishing iridescent blue-green colour. There are also acrocarps which form large rounded tufts or cushions in rock clefts. The bright yellow-green Bryoerythrophyllum ferruginascens, with older leaves and stems often a striking brick-red, is on lime-rich rocks. Anoectangium aestivum resembles a small Barbula, of a brilliant yellow-green. Gymnostomum aeruginosum has narrower dull green leaves. Grimmia torquata is a rather pale blue-green above, the dead stems dark below, the leaves with a short white hairpoint. These three can make large bulging tufts on steep or vertical wet rocks. They are not plants that can be reliably named without experience, or a microscope, or both. There are many other similar but rarer species, especially in the mountains of central Scotland. Bartramia pomiformis is a larger plant, with long sharp leaves of a bright glaucous green. Individual stems resemble those of a Polytrichum, though of about half the size. It also occurs rarely on shaded acid banks in lowland Britain. The round capsule resembles a tiny apple. All grow well here on mounted cultures. I have found crushed granite the must useful substrate, or peat. Traces of lime can be sprinkled on for the Barbula, and perhaps some neutral soil for Pohlia cruda and the Bartramia. They tolerate shade well, and if shaded, are not troubled by long periods of desiccation in summer. The most obvious liverworts in mountain clefts are often Conocephalum conicum, sometimes rather stunted, but still easily recognised by its smell, and the similar but red-edged Preissia quadrata. The Preissia can be grown like Lunularia, but is less tolerant of waterlogging than Marchantias. If it fails to flourish in culture, too wet a soil is a likely cause. Considering its habitat, Preissia is surprisingly tolerant of summer drought. Such damp crevices and overhangs are common at the base of mountain cliffs, and are always worth examining. There are thousands of growers who specialise in alpine flowering plants. Among alpine mosses there is an even greater range of habitat preferences, and an even greater range of challenges to horticultural skill. They occupy many niches where no flowering plants can gain a hold. One habitat which only the young and fit may ever see is the snowpatch flora of the highest Scottish mountains, where a specialised moss and hepatic flora is covered in snow for up to 10 or even 11 months a year. I had some plants from such habitats, mostly in the refrigerator. I hope this chapter has given some idea of the challenges, the mysteries and unsolved problems, involved in growing such plants. Yet the most casual visitor to the mountains may hope to find a few attractive species which can be kept without too much fuss, in a propagator, a greenhouse, or even a jamjar on a windowsill. And even one or two survivors make better mementos of our wild and wonderful mountain scenery than anything to be found in a tacky souvenir shop. |