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The Scottish Botanical Review No. 3] 1912 [ Juy The Geological Relations of Stable and Migratory Plant Formations. By C. B. Crampton, M.B., C.M., of H.M. Geological Survey. (Continued from p. 79.) PART V. THE GEOLOGICAL RELATIONS OF THE MIGRATORY PLANT FORMATIONS. THE great pile of sediments, dating from the Precambrian onwards, stands witness that erosion and deposition have prevailed throughout geological time. Stratigraphy has fully borne out Lyell’s dictum, that the geological workings of the past are to be measured by a study of those now in operation, and, for the purposes of the present argument, we may safely assume that the physiography of past epochs was governed by statical and dynamical factors approximately similar to the present ones. Sea-cliffs have always evolved at exposed points of the sea’s margin. Beaches have formed along the line of shore- drift from -places where cliff erosion afforded sufficient durable material to be pounded into shingle by the waves, but temporarily resist further dispersal. Sand has constantly accumulated in the shallower bays of exposed coast-lines, where the coastal currents slackened, and the sand, driven shoreward by the waves, has undergone exposure between tide-marks, to be captured by the winds, and built into VOLE. I: 127 IO 128 THE SCOTTISH BOTANICAL REVIEW coastal and travelling dunes. Mud-flats have always appeared in the protected estuaries of the larger rivers, or behind sand-bars in deltas, or shingle-spits traversing shallow bays where small streams find exit seaward. These various coastal formations have repeatedly evolved under certain recurring conditions of physiography, the results of the action and reaction of the static and dynamic factors of geology, and, apart from the effects of differences of climate and geography on plant growth and distribution, have, further, led to a similar range of habitats for the evolution of plant adaptation and association. With the same reservations the other agents of erosion and deposition have as constantly originated defined series of habitats for plant evolution the world over and throughout geological history. The streams have ceaselessly cut gorges and waterfalls, and laid down alluvial deposits of gravels, sands, and silty loams. So long as mountains have arisen, and passed away under the influence of erosion, so long have frost, insolation, and gravity conspired to produce alpine crags, screes, and landslips. But the sphere of these operations has undergone endless change. The geological agents desert their work barely begun, or but half accomplished, and start afresh elsewhere, only to return once again, after intervals measured by days, years, or centuries. From the very nature of their operations, these agents must have caused frequent disturbances in the more stable types of vegetation, whose character of stability, indeed, depends upon their absence. But other types, adapted to profit by less stable conditions of existence, or quicker to migrate and take possession of newly formed surfaces, have been ever ready to escape the biological or physical struggle for existence intensified in the areas of least disturbance, and thus have arisen plants and plant communities especially accommodated to the comparatively rapid changes of environ- ment attached to such conditions. With a climate favourable for vigorous vegetation, the plants that follow the track of the migratory agents include many that are forced to avoid the intense biological com- STABLE AND MIGRATORY PLANT FORMATIONS 129 petition of a mature succession, while in semi-desert condi- tions of drought or intense cold, the plants following these tracks frequently thereby escape physical extremes. The migratory agents originate habitats with, on the one hand, a surplus, or, on the other, a reduction of water, oxygen, and salts, over that available by the neighbouring stable vegetation. They may cause excessive transpiration, as in areas of blown sand or hinder absorption, as in salt-marshes ; they may palliate extreme conditions, as in deserts and arctic regions, and generally tend to delay the type of stabilisation under the climatic conditions prevailing. Mountains, seas, and large rivers may form barriers to the spread of certain stable types of vegetation, but the alpine, coast and river belts have always preserved open routes of migration and places of refuge for plants ousted from the neighbouring areas of competition. They form sanctuaries for relic associations, or outposts for pioneer invading species. These open ways and asylums may shelter plants that have lagged behind or degenerated in competitive stabilisation, preferring the easy existence of being continuously bathed in water, or of annually happening on fresh open formations. But the stations of the migratory formations in many cases are peculiar to the agents of surface change, and are occupied by endemic forms which have adopted lines of specialisation meeting the physical conditions of a peculiar environment, rather than those adapting them for competition over wide areas of stable topography. They have become nailed to a special physical environment, or have been forced to be constantly accommodating themselves to unstable and chang- ing surroundings. Thus we have lithophytes, aquatics, sand-dune, swamp and marsh plants, halophytes and various xerophytes, vagrants and annuals, excluded from the neighbouring stable formations. - Some survive or even flourish under rapid physical changes in the habitat, and many have specialised in their mode of growth, and in the nature of their fruits or seeds, particularly adjusting them for dispersal by the sea or rivers, by the wind, or by migratory animals. Many have doubtless evolved under the migratory conditions in which we find them, while others may be descendants of plants that had 130 THE SCOTTISH BOTANICAL REVIEW found refuge in stable areas, subject to climatic extremes, as drought or great humidity accompanied by low temperatures, but with amelioration of climate were liable to extinction by competition, unless they underwent changes rendering them more capable of rapid migration. Migratory formations do not, however, always show a complete change of species from the neighbouring stable formations, but may be partly stamped by a change in the type of growth, z.e. the habit of certain species, or perhaps by forms or variations, such as have not yet been sufficiently explained as fixed and inherited, as purely physiological and anatomical adaptations, or selected mutations. It seems, in fact, to be the rule rather than the exception that a species common in a stable formation, on appearing as a dominant in a neighbouring migratory formation, is under a different form, which is retained everywhere within the limits of the migratory formation. This, at least, appears to hold with Calluna vulgaris, species of Sphagnum, grasses, and some other plants. The migratory formations are naturally distributed in the field into :— 1. Those of the coastal belt. 2. Those of the stream belt. 3. Those of the foci where the physiography curtails vegetation and prevents stabilisation, owing to its influence on drought, wind exposure, low temperatures, or the instability of surface incurred through gravitation. In the coastal belt we find various formations depending chiefly upon reactions between the following geological factors :— 1. The nature of the rocks, and the initial topography of the surface entering the belt of erosion. The resulting configuration of the coast-line and coastal profile. Their comparative permanence or tendency to rapid alteration. 2. Recent positive or negative displacements of the coast- line and their influence on plant succession. 3. The submarine profile as influencing the fetch of the waves, and thereby, in particular, the range and character of the cliff vegetation. 4. The nature of the coastal currents in their influence on STABLE AND MIGRATORY PLANT FORMATIONS 131 the distribution of deposits, localising the shingle beach, sand- dune, salt-marsh, and marine algal vegetation. 5. The range of the tide in its influence on the marine algal zones and the salt-marsh vegetation. 6. The position of the river exits, as affecting the salinity of the waters, and the relations of river-borne and tidal deposits, of brackish and salt-water marsh and reed-swamp. 7. The influence of seaward drainage, weathering, and gravity on the coastal profile. The ratio of degradation by weathering to the advance of sea erosion. In the stream belt the principal factors are perhaps included in :— 1. The sources of the permanent water supply ; their nature and capacity, their distribution and seasonal variation. 2. The physiography resulting from the interaction of the drainage system and the surface, in the various segments of the torrent, valley, and plain tracts. The rate of flow, prevalence of erosion or deposition, sorting or silting, flushing or sustained submergence. The blown sand and salt-marsh formations of the coastal belt are described in the “ Types of British Vegetation ” (3), and our shingle beaches are at present undergoing careful analysis (38). The stream belt, apart from the fens (3) (25), certain lakes (39) (40), and moorland districts in Scotland (26), has at present received little attention in this country, owing partly, no doubt, to the extensive artificial alterations it has undergone. Our rock formations have also received some attention (3) (26). Many of these migratory formations, though perhaps not recognised as such, have been described by plant ecologists in various parts of the world. Rock formations have formed a special study in Switzer- land. The stream belt and coastal belt have been studied in America, New Zealand, Belgium, the Fardes, Denmark, and elsewhere. In the following generalisations, the migratory formations are treated chiefly from the geological standpoint, as much work is needed before an ecological classification of migratory formations can be considered as placed on firm foundations. The majority of them are perhaps included under Warming’s 132 THE SCOTTISH BOTANICAL REVIEW aquatic, helophytic, lithophytic, psychrophytic, psammo- phytic, oxylophytic, and rubble formations, etc. (13), but the desirability of further analysing them from the standpoint of physiography has doubtless been apparent to some ecologists for a considerable period of time. Aquatic formations always vary with the physiography. Rock formations may support certain common species over wide areas of different physio- graphy, but the majority show signs of being distinct in type and association with the physiographic factors leading to the rock exposure. Shingle beaches and alpine screes must obviously be separated, as habitats for plant life, and the meadows, marshes, and swamps of the higher and lower parts of the drainage system come under very different physio- sraphic conditions of existence, and vary widely in their plant associations. Certain types of plant association only follow in the wake of the migratory agents of surface change ; thus we have various spring, flush, marsh, aquatic, alluvial—meadow and swamp associations, confined within the sphere of action of the drainage system of the streams, rivers, lakes, and seas, the world over. Halophile associations are confined to the mari- time coastal belt or to places marking the present or late foci of centripetal, inland drainage. The latter may form zones around inland seas or lakes, or appear in the form of playas, dry lakes, and salt marshes. Alkali soils have a somewhat wider distribution than recent foci of centripetal drainage, especially in the desert areas subject to much erosion, as the salts are redistributed by the winds, and old salt deposits are frequently re-exposed at the surface. Hilgard has shown how the salts tend to accumulate at or near the surface of the soil in sandy, saline deserts, by the effects of evaporation bringing a considerable amount of the soil water to the surface. All spring associations have certain common factors in the water supply coming directly from beneath the surface of the ground and in being continuously changed, but various springs differ much in the volume and temperature of the water, the dissolved salts and gases, and other ways. These factors may completely suppress the growth of vegetation, only allow the presence of a peculiar flora, or cause an STABLE AND MIGRATORY PLANT FORMATIONS 133 association of species which individually grow in other habitats. Spring associations appear to be clearly demar- cated by the extent of the focus within which the waters retain certain definite characters, but where the waters have a fairly large and constant volume certain species may follow the watercourses for considerable distances. Spring plant associations are most evident in the mountainous districts of this country, since the original relations of the drainage and vegetation have usually there been less interfered with. High level springs with Phzlonotis, Epilobium alpinum, Saxifraga stellaris (3) (p. 326), etc., can be distinguished from springs in the moorland bogs with Hypuum revolvens, Sphagnum, Stellaria uliginosa, etc., and these again from springs arising on the lower alluvial terraces with Hypnum cuspidatum and others; but various stages can often be recognised leading from one to the other, while some show peculiarities of their own demonstrating that the plants are highly susceptible to conditions which vary at different springs, and which, as yet, have received practically no attention by plant ecologists. Groups of species, including one or another of the above, or of the following (Dzcranella squarrosa, Hypnum sarmentosum, Hypnum stramineum, Hypnum scorpioides, Hypnum commutatum, Amblystegium filticinum, Mnium punctatum, Bryum alpinum, B. pallens, L. Duvalit, Webera albicans, and species of Aneura, Scap- anta,and Sphagnum, Selaginella,Montia, Ranunculus, Myosotzs, Chrysosplenium, and others), are commonly met with in our moorland districts again and again in precisely similar surroundings, which are often difficult to define and need careful examination. In other words, the fact that the plants are aquatic or semi-aquatic, and that the water is flowing, will not define a spring association, but rather the tout ensemble of conditions as included in the physiography, not only in its direct physical influence, but also in its influence on the country’s fauna, whether this be as a home, death trap, barrier, or an invitation to drink. There is often a striking physiognomy in the floating carpet associations of gentle but constant springs, the mosses, hepatics, and phanerogams alike assuming a close-pressed, fastigiate growth, that is presumably to be explained as the result of 134 THE SCOTTISH BOTANICAL REVIEW an abundant water supply and the absence of disturbing factors to phototaxis. This is specially noticeable in species of the subdivision Callzergon of the genus Hypuum in some other mosses and hepatics, and in Mondza fontana and Stellaria uliginosa. Shallow channels leading from springs and others occupied by the surface run-off of water in wet weather may be entirely carpeted with vegetation, from the velocity of the current and mobility of sand or stones being insufficient to prevent a closed plant carpet. Such channels have been termed “ Flushes” by the writer, who has made a preliminary attempt at classifying those encountered in the moorland, as permanently wet (wet flushes), or periodically wet and dry (dry flushes), and also as acid, and calcareous flushes, according to the conditions of the waters (26). Further field examination of plant habitats that have ecological relations to flushing by water reveals the fact that flushed surfaces should be primarily subdivided into two groups :—(1) hard rock surfaces, and (2) surfaces capable of easy erosion by running water. The former may be com- pletely clothed with vegetation, though subject to torrential action, as may often be seen in waterfalls, where the whole rock face may be clothed with a special vegetation of mosses and alge. Rock surfaces with a comparatively constant but gentle trickling stream of water, and especially if vertical or nearly so, usually support an algal vegetation only, while others, only periodically flushed, form the stations of very defined associations of bryophytes and alge, varying from open to closed formations, and these again to open formations, with the results of progression and retrogression or reinitiation of plant succession induced by an increasing erosive power of the water as soil accumulates, and its tendency to migrate from point to point, deserting one part of the rock surface for another. The various stages of migration of a ‘‘ rock flush” are marked by different plant association, but the presence of certain alge and bryophytes, and the absence of lichens, except species of Verrucaria, etc., appears to specially characterise rock surfaces subject to flushing, as distinct from others only receiving atmospheric moisture. We must therefore distinguish ‘‘rock flushes” as a group STABLE AND MIGRATORY PLANT FORMATIONS 135 requiring separation from other rock habitats and from the moorland and woodland flushes, etc., on soils capable of easy erosion. The moorland flushes show relations to spring associations on the one hand, and to the grassland of the sandy river alluvia on the other, and many so-called bog plants are practically confined to these flushes and the alluvial stretches. The flushes form a connecting link and a route of migration between the springs and the grassland and swamps of the higher stream alluvia. On the slopes of some of our mountains the flushes are so numerous and so constantly migrating from one point to another, that large areas of grassland are formed through their influence, as mentioned above. The flushes arising from snow lie have well - defined characters of their own, as pointed out in the last number of this Review (41). Flushes are also encountered in woods, where they show a complete change in the plant association, including the trees. In this country the wet flushes in woods are commonly dominated by ash trees in oak woods and by alders in birch woods. The most frequent trees in flushes are the ash, alder, various forms of sallow and bird-cherry, and sometimes hawthorn, blackthorn, or hazel, but many flushes form open gaps in the woods occupied by what might be termed a spring-marsh vegetation. These woodland flushes are recruited from spring associations and from the bush swamps of the river alluvia. Not only has each type of river its natural history, but so has each segment of its course. The source in a snow patch, spring, or tarn, or from water-logged peat, affects in different ways the upper drainage waters and the plant associations. In their middle courses rivers form rock-chasms and waterfalls; but again there are differences in plant association, from differences in the nature of the waters or the rocky stream channel. The submerged and amphibious associations of the waterfalls, rocky gorges and boulders, always show a close zonation, depending upon the force and erosive power of the stream, the aeration of the water, the amount of light, the depth and permanence of the stream, eee 136 THE SCOTTISH BOTANICAL REVIEW and the range of spray. This may be well studied in the aquatic and semi-aquatic bryophytes and algz of our own moorland streams. The plants which colonise the deserted banks and crags are, further, always the same under the same physiographic conditions of exposure and substratum, and differ from the surrounding more completely stabilised vegetation. The segments undergoing erosion slowly migrate up- stream, alternating with alluvial stretches laid down on temporary base levels, where lateral erosion has prevailed over vertical cutting. The ailuvial deposits of such tem- porary base levels are chiefly composed of sands and gravels, or torn and washed-down sods, or undermined and subsided masses of peat or soil interwoven with roots. These various forms of alluvial deposits soon become colonised by plant associations differing completely from the surrounding vegetation. Parts which temporarily escape renewed erosion, form caps to a succession of terraces, as vertical cutting is renewed. So long as they remain subject to flooding, or differ in their physiographic relations to moisture, plant food, etc., from the neighbouring stable areas, so long will they bear character- istic plant associations, and meadow, marsh, bush, swamp, or other associations hold the ground, but with time the climatic soil-relations are restored and the ground is invaded by the associations of the dominant stable formations (26). The lakes which are interposed in the stream belt form rather more permanent base levels to erosion, and the vegetation of their waters and shores differs considerably from that in, or flanking running water. The plankton is, of course, more abundant, and probably varies much with the nature of the drainage basin of the entering streams, and with the physiography of the lake, as affecting the food supply, the depth, temperature, and other conditions of the water. The floating and submerged aquatic flora differs much from that of running streams, and varies greatly in the high-level tarns and moorland and lowland lakes (39), (40). The marginal plant associations further differ, according to the rise and fall of the waters, the amount of incoming silt, sand, or gravel, and other factors which require investigation. STABLE AND MIGRATORY PLANT FORMATIONS L377 In their lower courses rivers form wide alluvial plains of loams or silts, subject to flooding at seasons depending upon peculiarities in the environment of the river basins. Where the rivers become icebound in winter, the flooding in spring is accompanied by ice rafts, effectually preventing tree growth (13). Or the flooding may be due to the melting of the snows in early summer, or to autumnal rains. Unlike the subalpine alluvial terraces, the lowland flood plains remain subject to flooding for comparatively long periods, and owing to the sluggish nature of the widespread current are apt to accumulate silt over those parts nearest the river channel ‘These consequently become raised as natural em- bankments, hindering drainage from the lower marginal parts of the alluvial flats, which form swamps or marshes. The rivers also cut laterally and form oxbow windings, which, in course of time, often become deserted by the river waters, owing to short-circuiting of the main stream by further erosion. The deserted oxbows then often form natural ponds, and where beyond the sphere of the river floods, become filled up only through the growth and decay of vegetation and accumulation of humus. Unfortunately for British plant ecologists, the natural vegetation of the alluvial flood plains of our own rivers has been largely replaced by cultivation and artificially treated pasture. Our rivers are tamed and managed and only occa- sionally get beyond control. The banks are artificially raised, the oxbow windings are replaced by cut canals, and the formerly flooded tracts have been drained by pumping. The natural head and rise and fall of the waters has also been altered by drainage at their sources, and erosion is minimised by breakwaters, locks, floodgates, and mill-dams. Lately formed alluvial deposits generally have a greater surface soil fertility than the areas occupied by stable forma- tions. This is due to their filtering action on the soluble salts or silts supplied by the river waters. The climatic effects of leaching of the surface layers of the soil, which is so marked a factor in our stable formations, is of little con- sequence in alluvial soils until they have been for some time deserted by the river waters. This surface soil fertility favours surface rooting species, and especially grasses, the 138 THE SCOTTISH BOTANICAL REVIEW main disadvantage accruing to flooded alluvial tracts being the local tendency to stagnation and soil acidity. Their physical relations to drainage are moreover detrimental to deep root oxygenation, and the tree growth is generally of short stature in temperate regions and confined to certain species (13). When the deposits are well supplied with ground water, but porous and superficially well aerated, meadow prevails in temperate climates ; where less permeable and ill-drained, marsh-land or swamp. The type of meadow naturally varies with the physiography and the nature of the waters. In the moorland region of this country a subxerophytic type of grassland is commonly met with, but our lowland meso- phytic meadows have nearly all been much altered through drainage and cultivation. Extensive natural mesophytic meadows are said to still persist in Northern Russia and Asia, and form the habitat of some of the most striking species of herbaceous Umbelliferz (1). Reed-swamp is generally confined to a narrow fringing reed belt in our rivers, owing, no doubt, partly to artificial restrictions to the lower river courses, but extensive reed- swamps are widely distributed, according to Warming, and consist of such genera as Phragmites, Glycerta, Cyperus, Typha, and Sagittaria, and in tropical countries, of species of Caladium, Heliconia, Crinum, and others (13). Alder swamps and sallow swamps, according to the same authority, are universal in north temperate regions. And there, also, sallows and poplars fringe the streams in the steppes, while thorn forest forms a characteristic belt to those of desert subtropical zones. Black-gum swamps with Wyssa and Taxodium have been specially studied in the forest regions of the United States, and show peculiar conditions of the lower parts of the trunks and of the roots of the trees, the latter having a striking resemblance to the knee-roots of the mangroves of the coastal swamps. In tropical countries, forest swamps of various species of palms, bamboos, and aroids have been described. According to Schimper, “Kurz states that swamp forest is the most curious forest in Burma, and of great interest to the botanist. In fact, its constituent plants are so dissimilar to those of the STABLE AND MIGRATORY PLANT FORMATIONS 139 surrounding forests that one must necessarily ask how all these trees come here. The greater part of them do not occur anywhere but in swamps or similar watery places. Swamp forest is completely bare in the rainy season, and it occurs in typical form in places, which in the rainy season are covered by water up to 4-5 feet (sometimes even 7 feet). It consists, like rain-forest, of several tiers: tall trees 60-70 feet high, small trees, shrubs, and plants clothing the ground ” (1). Alder and sallow swamps are widely distributed in this country, and patches of fenland still characterise some of our lower river courses. The fenland growth is apparently dependent on certain topographic factors regulating the water level and protecting the area from erosion and silt. For its full development fenland may have somewhat similar climatic requirements as the moorland, but owing to its developmental relations to physiography, is probably capable of forming far beyond the moorland climatic province. The physiographic relations of the swamps, fen, and the woodlands known as “Carr,” which are found in our principal fen district of East Norfolk, are set forth in the “Types of British Vegetation,” to which the reader should refer. Within the tidal way of our rivers, the reed belt generally consists of different species to those found further up stream. Fringing belts of Sczzpus lacustris, Sparganium ramosum, Heleocharis palustris, Carex aquatilis, and others, with back- waters and swamps of 7ypha, Alisma, Phalarts, etc., give place to such species as Scirpus maritimus, Carex salina, Scirpus triqueter, and others (39). Alluvial meadows with Poa, Dactylis, Holcus, Atra cespitosa, etc., to others with Hordeum maritimum, Bromus mollis var. glabrescens, or mari- time forms of Phleum pratense, Agrostis, and Triticum. Marshes with /uncus effusus, Juncus acutiflorus, Iris Pseuda- corus, Alopecurus geniculatus, etc., are represented by others with Juncus Gerardi, J. maritimus or J. balticus, Plantago maritima, Triglochin maritimum, etc., and from this we pass seaward to the salt-marshes of the estuarine mud-flats covered by the high spring tides. These have a close physiographic relation to those parts of the coast-line where the rivers deliver their burden of sands 140 THE SCOTTISH BOTANICAL REVIEW and silts. Mud-flats occur where the delivery of silt by the rivers is greater than the marine currents can dispose of or where the physiography prevents its dispersal. Mud accumu- lates in the protected estuaries of big rivers where the coast- line is indented and behind sand-bars or shingle spits in the rather more exposed positions, the barrier in such cases forming the forefront of a delta, or extending across the mouths of bays where smaller rivers debouch. Through changes in the position of the barriers, the areas forming such bays have sometimes been alternately occupied by the sea with mud-flats and salt-marshes, and by brackish and fresh water, marsh, reed-swamp, and fen, fully demonstrating the migratory and unstable nature of such plant formations. Parts of what were originally extensive marshes bordering on exposed coast-lines, like the Romney Marsh and Pevensey Levels in the south of England, are at present somewhat lower than the high-water mark of spring tides, but are protected from the sea by a barrier of shingle extending across the coastal margin of the marsh. The history of the evolution of the Pevensey Levels has been much obscured through the prolonged interference by man, but from the evidence of borings (42), and from that of the submerged forests exposed at low water along the coasts, there is some reason for thinking that the areas of these levels, during one stage of post-glacial time, were largely covered by forest, the sea level being then lower than at present. With a gradual advance of the sea and, perhaps, a deterioration of climate marking a phase of moorland extension, the forest seems to have been locally swamped and buried in fenland peat, a great part of the area at length becoming submerged by the sea and covered with sand and silts. It would be at about this time, no doubt, that the great shingle accumula- tion of ‘‘ The Crumbles,” near Eastbourne, with its numerous parallel ‘‘fulls’’ or ridges and hollows, began to form, and a bank of this shingle probably prevented the sea from enter- ing the smaller Bourne Level, which is separated from the Pevensey Level by a ridge of higher ground. Pevensey is supposed to have still been reached by the sea in historic times, and previous to, and since that time, the Pevensey Level must have been successively mud-flats, salt-marsh, and STABLE AND MIGRATORY PLANT FORMATIONS I4I reed-swamp, the while the gradual eastward extension of a spit of shingle from the ‘‘Crumbles,” further and further, embayed the silts brought down by the streams, and turned the exit of the drainage further and further to the east. The greater elevation of the most recently formed fulls may point to a slight rise in sea-level since the marshes were reclaimed, but the levels have in all probability recently subsided over wide areas owing to artificial drainage and interference with the rivers at their head waters and points of exit seaward. Salt water still percolates through the shingle barrier at high water and affects the plant association in the adjoining marsh ditches. Apart from areas of wind erosion, sand only accumulates at temporary base levels in the swifter courses of streams, in lakes entered by such streams, and in bays or near river exits on exposed coast-lines. The plant associations which take possession of the sand depend partly on its mineral composition and humus content, but chiefly on its physio- graphic relations to flooding or water-level, the fairly constant or rapid rise and fall of the latter, and the nature of the water, stagnant or otherwise. Plant associations on sand alluvia may vary, according to these conditions, from open formations to grassland or heath, from marsh to bush swamp. Accumulating sand is subject to wind drift and dune formation, but this only occurs to any extent in this country in connection with lakes and the sea coast. The plant associations following such blown sand are of an entirely different nature to the stable vegetation on sands in this climate. The former are specialised for obtaining their water supply at a depth and for resisting sand erosion and overcoming sand burial (43), whereas the latter are plants that can live on superficially leached soils subject to periods of drought and with a limited tendency to accumulate acid humus. Flood gravels and shingle beaches are peculiar to the swifter reaches of rivers and to sea coasts. Those of recent accumulation rarely shelter any vegetation, but where less liable to frequent movement they are generally covered with species of encrusting lichens capable of growing on very smooth, hard surfaces subject to periods of drought and 142 THE SCOTTISH BOTANICAL REVIEW insolation. The lower layers of shingle are usually moist, like the crevices of rock, owing perhaps to protection from evaporation.! Shingle banks in rivers often support a very varied open association of mixed annuals and perennials, vagrants and colonists from neighbouring associations. Such open associations may show a mixture of plants with very different requirements for water, which is often abundant at a short distance beneath the surface. The older river shingles in moist, exposed moorland districts accumulate acid humus owing to the growth of certain species of mosses in the crevices exposed to light, but in the more sheltered and warmer positions they frequently become occupied by thorn scrub, including species of rose, sloe, whins, and brambles, with often honeysuckle, elder, broom, and others. In the upper courses of many of our moorland streams the alluvia often consist of great stretches of shingle due to the erosion and sorting by the stream of drift full of boulders and stones of various dimensions. These shingles remain barren if the materials are well assorted, and consequently mobile during conditions of flood, but where many boulders occur the intervening hollows are often filled with fine gravel and sand, and the part of the bed which is deserted when the stream is low forms a scattered open formation of lithophytes on the boulders and sand-dwellers in the hollows. These are chiefly plants that can withstand flooding and some amount of scour, such as Rhacomitrium aciculare on the boulders, and species of Sagzna, Bryum, Polytrichum, etc., in the hollows. It is on these shingle stretches, moreover, that certain alpines, especially those which frequent springs or flushed ground, such as Epilobium alpinum, Saxifraga stellaris, and Alchemilla alpina, may often be found several miles from the sources of the streams where their centres of distribution occur. Shingle stretches of this nature naturally never become grassland by any kind of plant succession, except at the tails of the banks, which often consist largely of sand, or in old deserted river loops which have become choked with fine 1 See, however, ‘‘The Shingle Beach as a Plant Habitat,” by F. W. Oliver, ‘“The New Phytologist,” vol. xi, No. 3, March 1912, p. 98, where the water problem of shingle beaches is discussed, and where the suggestion is made that it may depend upon the formation of internal dew. STABLE AND MIGRATORY PLANT FORMATIONS 143 debris. Grassland is, however, frequently built up on moor- land shingle stretches by the dumping of sods carried down stream. Such sods usually consist of the resistant upper layers of peat, matted with roots, but the original peat flora always dies off when subjected to this treatment, and gives place to Carex Goodenovit, Nardus stricta, or other species. The sods gradually accumulate until a somewhat uneven surface becomes covered with grasses, sedges, and mosses, and eventually, when deserted by ordinary floods, forms a fine pasture in which Axthoxranthum, Festuca, and Agrostis are prominent species. From gravels and shingles to the wide stretches of coarse rock debris of the alpine screes and mountain plateaux might appear but a short step, so far as the nature of the surface as a habitat for plants is concerned. The material which forms this debris has not, however, been through the mill of picking for wear and tear that has eliminated all softer material in the former case. The material is angular, formed by frost, and subject to further splitting and reduction by the same agent. The surfaces, though rougher than the pebbles, are less permanent as a basis for lichens, and are further subject to frequent abrasion from slipping or sand blast. Where long undisturbed, on the flatter summits, lichen growth is, however, rapid on account of the brief spells of drought, and may extend to the foliaceous and fruticose types of development. The barrenness of screes and mountain top debris, like that of shingles, is, no doubt, partly due to superficial drought preventing the growth of shallow-rooted perennials and especially their seedlings. It is noteworthy that the plants of shingles and porous rock debris are often such as have fruits liable to lodge near the surface owing to their size or adhesiveness preventing them from being carried deep into the debris. Small seeds would have little chance of survival on germinating. Other plants of these places have highly developed underground rhizomes or roots, with great powers of searching for water and for replacing subaerial parts which undergo destruction. The barrenness of screes is further due as much to instability inducing land- slip as to the porous nature of the surface, while that of the VOL. I. II 144 THE SCOTTISH BOTANICAL REVIEW mountain top debris, apart from its porosity, is chiefly the result of the intense evaporation and erosion caused by wind. Scree plants are those that can find their water at a depth by means of rhizomes and can send up shoots to the light of day despite the slipping of the surface. The plants of the plateaux debris, on the other hand, depend chiefly on their powers of resisting desiccation, erosion, and bodily removal by the wind. Block screes are highly favourable for the growth of special types of lichens and bryophytes. The blocks long resist removal from the position where they come to rest, but the surfaces are exposed to the maximum of light and atmospheric precipitation and undergo slow decay, while the general surface is for long quite uninhabit- able by higher plants. Rock formations are mainly the results of stream erosion, coastal erosion, or position in relation to gravity, frost, and poverty of vegetation. They may therefore be roughly classified into : (1) Stream gorges and waterfalls, (2) Coastal cliffs and platforms, (3) Alpine crags. All these are naturally migratory under the influence of the geological agents, their surfaces being liable to destruction, whereupon a fresh initiation of plant succession is invited (44) (3) (26). In the case of stream gorges the type of rock vegetation furthest removed from the influence of the stream depends on the physiographic relations of the rock to the sun, wind, and frost, and its chemical and physical relations to leaching, water capacity, and drainage. The lower parts of the gorge under the influence of spray, flooding, or erosion, each have their own type of vegetation, which may further depend on the amount of light, the aeration, and the acid, neutral or alkaline nature of the water afforded by the up-stream part of the drainage basin. The vegetation of sea-cliffs is perhaps even more complex, since the late relative displacements of sea-level and the structure of the rocks in their relation to sea erosion in forming vertical cliffs plunging directly into deep water, or more irregular cliffs with the accumulation of beach at their base, has a marked influence on the range of the vegetation and its composition (26). STABLE AND MIGRATORY PLANT FORMATIONS 145 In the vegetation of the cliff top, the coastal profile is often of first significance, and. besides this, the influence of the chemical and physical relations of the rock forming the cliff, to leaching, water capacity, and drainage, all require attention. Alpine crags primarily owe their features to the slow effects of frost, insolation, and gravity, but many of the crags of mountainous regions, including most of those in this country, have been further influenced by glaciation. The late glacia- tion has led to rock exposures in places where frost, insolation, and gravity now only conspire towards their burial, and, on the other hand, has reduced elevated summits where such agents would be most active in erosion to rounded debris- strewn contours. The foremost tendency of these agents is towards obliterating the effects of glacial erosion, eliminating the crags on gently sloping ground and at lower levels, and forwarding the development of those on the steeper contours at high elevations. In the former case, the succession of plant associations has full stabilisation as a goal in sight ; in the latter, only true migratory associations can obtain a footing. In the latter, the true alpine crags, all the associa- tions, lithophytes or chomophytes, hold but temporary habitats liable to destruction by disruption and landslip. As in the case of all crags and steep banks, the more elevated and exposed positions forming the tops and spurs are specially liable to leaching and drought, while the lower parts of the faces and protected crannies obtain the more permanent supply of water and food solutions which descend the surfaces and crevices of the rocks. The former are leached by atmospheric precipitation, rapidly drained, and exposed to insolation and the drying influence of wind, while the latter are more protected from sun and wind, and obtain the food materials and water draining from above. This influence on plant distribution, which may be studied on any roadside wall, extends to lithophytes, chasmophytes, and chomophytes alike, but varies much with the chemical and physical relations of the rock to leaching. In conclusion, it may be said that all rock plant associations are apt to differ according to their relations to leaching, water capacity, flushing, drainage, and exposure to the sun. Alpine 146 THE SCOTTISH BOTANICAL REVIEW crags are specially influenced by frost, wind, mist, drip, and snow lie ; the coastal crags by erosion, salt spray, insolation, wind, and manuring by sea-fowl, and river crags by erosion, inundation, spray, and the degree of exposure to light. REFERENCES. (38) Otiver, A. W.—“ The Shingle Beach as a Plant Habitat.” The New Phytologist, vol. xi., March 1g12. (39) SmiTH, R. and W. G.—‘‘ Botanical Survey of Scotland : Forfar and Fife.” Scot. Geograph. Mag., 1904. (40) West, G.—“ A Comparative Study of the dominant Phanero- gamic and Higher Cryptogamic Flora of Aquatic Habit in Three Lake Areas of Scotland.” Proc. Roy. Soc. Edin., vol. xxv. part. x1, 1904. West, G.—‘‘A Further Contribution to a Comparative Study of the dominant Phanerogamic and Higher Cryptogamic Flora of Aquatic Habit in Scottish Lakes.” Jd7d., vol. XXX. part ll., 1909. (41) SmitH, W. G.—‘ Anthelia: An Arctic-Alpine Association.” Scot. Bot. Review, No. 2, April 1912. (42) TopLey, W.—‘ Geology of the Weald.” Memoirs of the Geological Survey of England and Wales. Reip, C.—‘‘Geology of the Country around Eastbourne.” Memoirs of the Geological Survey of England and Wales. (43) For the physiographic ecology of sand-dunes see in particular Cockayne. (44) OETTLI, M.—“‘ Beitrage z. Okologie der Felsflora,” Ziirich, 1905. Caithness Lichens. By Rev. D. Lillie, B.D. THE following is a list of lichens gathered by me in Caithness (v.c. 109). Inthe case of some of the rarer species which I have gathered only once or twice, I have stated the locality. I have to thank those who have assisted me in determining the specimens. I am especially indebted to Dr. Bouly de Lesdain of Dunkerque, France, who has examined for me a CAITHNESS LICHENS 147 large number of specimens and has furnished me with interesting notes and sketches and dimensions of spores of a considerable number of rare or critical species. Lichina pygm@a Ag. (Fresgoe, Reay). » confinis Ag. (frequent). Collema flaccidum Ach. a tenax Ach. (frequent). » mugrescens Ach, Leptogium lacerum Gray. he scotinum Fr., var. stnuatum Malbr. Spherophorus coralloides Pers. = SJragilis Ach. Beomyces rufus DC. a aeruginosus DC. (frequent). Stereocaulon paschale Fr., teste Bouly de Lesdain. - denudatum FI. Pycnothelia papillaria Duf. (rare). Cladonia firma Nyl. » pyxtidata Fr. -, is var. neglecta Fl’k. ¥ ed var. gracillima, teste B. de Lesdain. - - var. costata, teste B. de Lesdain. » jembriata Fr. - re J. subulata. on - J. dendroides. i var. Lubeformis Fr. » jrbula Nyl. » gracilis Hoffm. a cornuta Fr. ss sobolifera Nyl. = degenerans F\. i . Ss. pleolepidea Ny\. (Morven). » furcata Hoff. _ » var. spznosa Hook. Bs racemosa Ny}. ie 5, | ferecuroa ds. a 2 var. fissa, teste Bouly de Lesdain. » pungens FI. iS crispata Nyl. 148 THE SCOTTISH BOTANICAL REVIEW Cladonia crispata, var. cetrarieformis (DC.) Nyl. 3 squamosa Hoffm. - coccifera Schaer. 5 bellidifiora F\. > digitata Hoffm. = deformis Hoffm. 5 macilenta Hoffm., var. coronata Ny). 6 Floerkeana Fr. Cladina rangiferina Ny). 33 is f. tenuis F\. : sylvatica Ny). “s impexa Harm., teste Bouly de Lesdain. uncialis Ny}. Ns , J adunca Crombie. , amaurocrea Ny). vd bs jf. cylindrica Schaer. Ramalina calicaris Ny}. FS farinacea Ach. (abundant). . Sraxinea Ach. (frequent). . s var. ampliata Ach. . fastigiata Ach. c. scopulorum Ach. (frequent). 55 subfarinacea Ny. a cuspidata Ny. (common). . ze var. tuberculosa Oliv., t. B. de Lesdain. 3 Curnow Crombie. minuscula Nyl., teste Bouly de Lesdain. Usnea florida Ach. , trta Hoffm. , dasypoga Nyl., var. plicata Ny}. Alectoria gubata Ny). + = bicolor Ny}. Cetraria tslandica Ach. (not common). » aculeata Fr. (common, occasionally with fruit). Platysma ulophyllum Ny). 5 glaucum Ny). Evernia prunastrt Ach. Parmelia saxatilis Ach. ‘3 » f furfuracea Schaer. . sulcata Tay). CAITHNESS LICHENS 149 Parmelia omphalodes Ach. - # var. panniformrs Ach. 5 Deliset Nyl., var. tstdiascens Ny). % Juliginosa Ny). % i var. /etevirens Ny. a lanata Walk. tristis Ny). physodes Ach. Sau Suliginosa Ny}. Lobarina scrobiculata Ny}. Lobaria pulmonaria Hoff. Ricasolia amplissima Leight. + letevirens Leight. Nephromium levigatum Ny|. Fe parile Ny\. (Dunbeath Strath). . lusttanicum Ny). Peltigera canina Hoffm. é rufescens Hoffm. 5: 3 var. pretextata F1. . scutata Leight. - hortzontalts Hoffm. Physcia parietina De Not. ‘. A }. chlorina (teste Bouly de Lesdain). - rn var. aureola Nyl. » btychnea Nyl. » pulverulenta Nyl. 2 . FJ. argyphea Ny. " ds var. angustata Nyl., teste B. de Lesdain. ss aquila Ny). , aguila var. cesio-prumosa Lamy, “new for Britain,” teste Bouly de Lesdain, “Bulletin de la Société Botanique de France,” tome lvii., p. 31... Clyth). » stellaris Nyl., var. leptalea Ny). tenella Nyl. atpolia Ny). » &tthotea Nyl. ulothrix Nyl., var. virella Crombie. ie proboscidea Ach. 4 cylindrica Ach. (frequent on higher hills). 150 THE SCOTTISH BOTANICAL REVIEW Gyrophora stipitata Nyl. (B. de Lesdain), new for Britain, teste Boul. de Lesdain. (Ben-na-bad.) x torrefacta Crombie. . hyperborea Ach. (frequent). . polyphylla T. and B. is flocculosa T. and B. polyrhiza Krb. Pannaria brunnea Ach. Lecanora hypnorum Ach. i saxicola Ach. ee iP var. aiffracta Nyl. 3 gelida Ach. (Camster Cairns). b, elegans Ach., var. tenuzs Ach. i murorum Ach. tegularis Nyl. i. obliterans Nyl., “nouveau pour |’Angleterre,” teste B. de Lesdain, “ Bull. Soc. Bot. de France,” tome liv. p. 443. % sympagea Nyl. . cirrochroa Ach., teste Bouly de Lesdain. i lobulata Somm. * vitellina Ach. ; epixantha Nyl., teste Bouly de Lesdain (Swiney). 2 citrina Ach. » Jerruginea Nyl., var. festzva Nyl. cerina Ach. ‘5 pyracea Nyl. i luteoalba Ny). : trrubata Nyl. a exigua Nyl. 55 galactina Ach. 5 dispersa Nyl. is subfusca Nyl. 3 : var. campestris Ny. _ var. glabrata, teste Bouly de Lesdain. 55 chlarona Nyl. 3 albella Ach. om glaucoma Ach. 5 prosechoides Ny. . sulphurea Ach. CAITHNESS LICHENS I51 Lecanora orosthea Ach. ” coniz@a Ny. symmuctera Nyl. polytropa Schaer. entricata Ny. erystbe Nyl., var. cénereo-fusca Crombie, teste Bouly de Lesdain (Lynegar). spodopheiza Nyl., teste Bouly de Lesdain, “ Bulletin de la Société Botanique de France,” tome lvi. p. 170. Miss A. L. Smith in the “ Reports of the Lichen Exchange Club, 1910,” expressed doubt as to the correctness of this, but Dr. Bouly de Lesdain, in a recent letter, says he still thinks it correct. The only other locality is in the island of Jersey. (Maritime rocks, Forse and Sarclet.) syringea Ach. atra Ach. badia, Ach. coccinea Crombie. ventosa Ach. tartarea Ach. a var. gonatodes Ach. (with fruit!), teste Bouly de Lesdain, “ Bulletin de la Société Botanique de France,” tome lvii. p. 32. (Ben-na-bad.) subtartarea Ny. parella Ach. cinerea Somm. (Aspicelta) Lilet, B. de Lesdain in “ Bull. Soc. Bot. France,” liii. p. 515 (Ousdale). gtbbosa Nyl. subdepressa Ny]. (Langwell). Dicksoni Ny. lacustris Fr. fils. rufescens Ny. discreta Nyl., teste Bouly de Lesdain (Achow). Pertusaria monogona Nyl., teste Bouly de Lesdain (Dunnet ” Head). globulifera Ny. 152 THE SCOTTISH BOTANICAL REVIEW Pertusaria amara Ny). (frequent). ie communis DC. a dealbata Nyl. # “ forma corallina, Crombie. i pustulata Ny). Lecidea coarctata Ny}. » granulosa Schaer. » parasema Ach. » goniophila Schaer. , enserena Nyl., teste Bouly de Lesdain (Scaraben). , fuliginosa Tayl. » contigua Fr. ; " var. platycarpa Fr. , erustulata Koerb., teste B. de Lesdain (Lynegar). » confluens Ach. cs lapicida Ach. » bithophila Ach. Bs * J. ochromeliza Nyl., teste B. de Lesdain. es lactea F 1. » plana Nyl. » fuscoatra Ach. , vrevulosa Ach. » grtseoatra Schaer. » @ilutiuscula Ny). a instratula Nyl|., “nouveau pour |l’Angleterre,” teste Bouly de Lesdain, “ Bull. de la Soc. Bot. de France,” tome liv. (1907) p. 444. (Camster Cairns and Dirlot.) Biatorina ceruleo-nigricans A. L. Sm. P Griffithi Mass. Ey premnea A. L. Sm. : chalybeta Mudd. Bilimbia Naegelit Auzi, teste B. de Lesdain. s sabuletorum Br. and R. Bacidea effusa Am., var. c@stopruinosa Mudd, teste B. de Lesdain. Bs arceutina Br. and Rostr., teste B. de Lesdain. " umobrina Br. and Rostr. Buellia verrucolosa Mudd. 53 stellulata Mudd. ” CAITHNESS LICHENS 153 Buellia disciformis Mudd. a contops Th. Fr. 5 atrata Mudd, teste B. de Lesdain Rhizocarpon alboatrum Th. Fr. - es forma ambiguum Leight. geographicum DC. petreum Massal. obscuratum Massal. “! lotum Sitzbrg., “nouvelle pour |’ Angleterre,” teste Bouly de Lesdain, “ Bull. Soc. Bot. de France,’ tome lili. p. 517 (Ousdale). Arthonia gregaria Koerb. radiata Ach. fe paralia Ny}., teste B. de Lesdain (Forse). a varians Ny. Endive: B. de, lkesd., <; Bull: .“Socs Rot SOSA tL = Hh xX / SSR ‘ . SNCS cs SEES = SSS Lo pee ~ altars: = ~ = = = : = Si PEATE A, R. Horwoop. +29 Jw bos vwol diiw bas sie lwmiec rat" bas marino woA) ensayo Inf to aqy teosben wold poomale=.. ;liziq= A (ege git 2081 zg .itiv Sq , sts paromupastd soitA) noivsarh iD a r ok ay axi as" Fs Yo : dims @ zolumulg= 4 ; eleydgoqed = AP vp ere A. B. floawoon. ; Prave Ti. PLATE II. Fig. 1. Lemna minor, Linn, Plant natural size, and with flower and fruit en- larged to show reduced types of floral organs. (After Bentham and Hooker, ‘‘ British Flora,” 1865, fig. 939.) 2.=pistil; s¢.=stamen ; sp. =spathe ; si. =sheath. Fig. 2. Phragmites eningensis, A. Br. (After Lesquereux, zézd., pl. viii. figs. 1, 2.) Tertiary, Golden Canon City, N. America, Fig. 3. Stages in the development of the embryo of Capse/la bursa pastoris. sp. =suspensor; cot,=cotyledon; 4.=hypophysis; #.=plumule; to show division of cells in suspensor for comparison with epibasal quad- rants in Jungermanniesz. (After Strasburger, ‘‘A Text-book of Botany,” 1903, fig. 399.) Fig. 4. Arundo goepperti,? Miinst. (After Lesquereux, zézd,, pl. viii. fig. 3.) Tertiary, Golden River, N. America. Scottish Botanical Review. | ; Q Winseg Wseeee) A. R. Horwoop. PLATE Le RECENT ADDITIONS TO THE CAITHNESS FLORA I8I Recent Additions to the Caithness Flora. By Arthur Bennett, A.L.S. THE Rev. D. Lillie of Watten Manse wrote me that his daughter, Miss Isabel Lillie, had collected in Caithness in rg1o and sub- mitted her specimens to Dr. J. W. H. Trail of Aberdeen. Dr. Trail has kindly sent me a list of what seem additions, though many are simply casuals or aliens :-— Nasturtium microphyllum, Reichb.—Watten Loch. 7 Geranium Pheum, L.—Outside garden, Lybster. 1 Trifolium agrarium, L.—Pasture, Stanstill, Bower. Lathyrus montanus, Bernh., var. ¢enutfolius (Roth).—Banks of Reisgill Burn. * Rosa rubiginosa, L. * Saxifraga umbrosa, L.— Among trees, Lybster. * Sedum album, L.—Old wall and bridge, Dunbeath. * Sedum stoloniferum.—Wall in Castletown. Callitriche vernalis, ..—Loch Watten. Adoxa moschatellina, L.—From South Caithness in 1908. * Campanula latifolia, L.—Weed in manse garden at Watten. 7Linaria Cymbalaria, L.—Garden walls, Swiney, Lybster. 7Z. vulgaris, L.—Old garden, Dunbeath. | Mentha piperita, L.—Forse, Latheron. Utricularia vulgaris, L.—Probably not characteristic. Carex curta, Good. ? + Bromus racemosus, L. The following have been found by other collectors :— Viola Lloyd, Jord.—Thurso. “Anns. Scot. N. Hist.,” rg11, p. 98. Trifolium arvense, L.—Edge of oatfield, Milton, near Wick. Mr. A. Henry sp. 7 Lamium maculatum, L.—Roadside, edge of a wood at Castletown. Mr. A. Henry sp. Melampyrum pratense, L., var. montanum (Johnst.).—Scouthall wood. Dr. Davidson sp. These comprise about nine real additions. Mr. C. B. Crampton has published ‘The Vegetation of Caithness considered in relation to the Geology” and there has added the undermentioned species to its flora :— Corydalis claviculata, DC.—In a few places along the banks of the Langwell and Berriedale Waters. This is an interesting addition to this northern flora; it seems wanting in all Sweden, occurs very locally in W. Norway (Slavenga) and S. Norway (Christianssand), in Denmark in several places, and North Germany, but not recorded 182 THE SCOTTISH BOTANICAL REVIEW for Finland, the Faroes, or Iceland. Occurs in East (Grant sp.) and West Sutherland (Marshall sp.). Filago minima, Fr.—Sandy places along Berriedale Water. On record for Ross and E. Sutherland, but not further north. Unknown in Finland, boreal Norway, and boreal Sweden. Vaccinium uliginosum, L. — Northern flank of Small Mount (1750 ft.), in the Langwell Forest. Found in Sutherland, Orkney, and Shetland !. Vaccinium Oxycoccus, L.—In the Langwell Forest, near the Dubh lochs of Skielton. Recorded up to E. Sutherland (Marshall, 1909). Milium effusum, L.—In the Achorn Gorge near Dunbeath. In E. Sutherland. Grant sp. Melica nutans, L.—Rocky banks of the Berriedale Water with birch scrub; scarce. W. Sutherland (Marshall). Bromus ramosus, Huds.—Achorn Gorge, near Dunbeath, and on the landslip beneath the cliff near Borgue. ‘This is not an addition, though so given, but it being recorded under the name of B. asfer, Murray, no doubt led to the mistake. It was found by Robert Dick at Dirlot, and I have seen it from the Forss Water. Asplenium viride, Huds.—Rock crevices on Smean (1500 ft.). In E. and W. Ross and Shetland. The above are an addition of seven species to the flora. The work whence these are taken enters fully into the ecological conditions of the plant-formations of Caithness from the top of Morven to the sea-coast. The most interesting plant as regards Scotland, /zerochloe borealis, is not mentioned. We know from Robert Dick that the plant occurs along the Boulder Clay of the Thurso river, but it would have been of interest if the occurrence of the species had been noticed from the geological standpoint. Mr. Crampton gives localities for other Caithness plants which are not localised in any of the published lists, as— Carex limosa, 1..—Small loch in the corrie at Yarehouse, where it grows associated with C. dioica, L., and C. paniculata, L. Ranunculus auricomus, L.—Mr. Lillie of Swiney, Lybster, has sent me a specimen of the above species, gathered by one of the children of Boultach School, and brought to Miss Hamilton, the teacher. This is an interesting addition to the flora, as it is not on record north of Nairn on the east coast, and of Argyll! on the west coast. In Sweden its distribution is continuous from Skane to Swedish Lapland, in Norway north to 71° 8’, and in Russian Lapland to 69° N. lat. It also occurs in the Faroes, but not in Iceland. SHORT NOTES 183 Short Notes. (Zt 2s hoped that all will combine to make this section as complete as possible by the prompt recording of all ‘‘ new records,” etc.) Hierochloe odorata, Wahl.—I should like to correct a mistake regarding the refinding of A/zerochloe odorata recorded by Don from Glen Calla. Mr. Arthur Bennett, in the ‘‘ Annals of Scottish Natural History,” October 1911, refers to a post-card he had received from the late Mr. A. Somerville, dated 14th June 1g04, in which Mr. Somerville states that he possessed a letter from Mr. J. Smith Nicoll of Arbroath regarding this plant. In the letter Mr. Nicoll says that he knew a Dundee botanist who had found /fzerochloe in Glen Calla. I have spoken to Mr. Nicoll on the subject, and he tells me that the botanist he referred to was Mr. William Smith, who, however, informs me that there must have been some misunderstanding, as he has never seen /Yzerochloe, and Mr. Nicoll himself says that he has been mistaken as to the plant found by Mr. Smith. On several occasions in May of this year I searched the Glen, but without success. R. H. CoRSTORPHINE. Mr. G. C. Druce (“Journal of Botany,” June 1912), in a note upon Alchemilla acutidens Buser, discovered on Ben Lawers last summer by Dr. Ostenfeld, refers specimens collected by Mr. E. S. Marshall at Inchory, Banff, and by myself in Linlithgowshire in 1910, to that species, and quotes Lindberg’s descriptions of this and A. alpestris Schmidt, with which it has formerly been confused in Britain. It would be well if Scottish botanists would pay special attention to the genus, as A. acwtidens may be expected in many other counties. There is also another very distinct-looking plant which occurs in Linlithgowshire for which I have been unable to obtain a name so far. M‘TaccGart Cowan, Jr. NOTE ON THE CALLUNA-MaAT ASSOCIATION OF THE MOUNTAIN Tops OF THE NORTHERN HIGHLANDS.—Some description of this plant association was given in the ‘‘ Vegetation of Caithness” (1911), and it is hoped in the near future to publish a fuller account of its geologi- cal and other relations as found in the Ben Armine district. Here we wish to draw attention to the habit of some of the typical plants of the association. These include, Cal/una vulgaris, Erica cinerea (frequent), Arctostaphylos alpina and A. uva-ursi, Thymus Serpyllum (frequent), Azra flexuosa, Azalea procumbens, Lycopodium alpinum, Antennaria dioica, Carex rigida, and species of Vaccinium occur sometimes. 184 THE SCOTTISH BOTANICAL REVIEW Some of these plants are normally creeping and prostrate, and form adventitious roots, e.g. Lycopodium alpinum and Carex rigida. But it is found that a similar habit is also common to Cad/una vulgaris, Erica cinerea, and Aira flexuosa, as well as the species of Vaccinium and Arctostaphylos. The plants all grow prostrate in the direction of the prevailing winds, and are subjected to conditions comparable to the layering used by gardeners for the propagation of many garden plants. ‘The wind continually erodes the surface where the plants are old and woody, thus destroying them, but the younger and more branched parts of the plants are buried in drifted material, thus inducing the formation of adventitious roots. This process results in a constant migration of the plants in a definite direction before the wind, and also leads to the peculiar wave-like troughs and ridges already described in the “‘ Vegetation of Caithness.” The type of Calluna is probably the form Z£7kae of P. Graebner, since it shows the geotropic curved extremities of the smaller branches. C. B. Crampton and M. MaccRrEcor. Dear Mr. Epiror,—It seems impossible to arrive at a full know- ledge of the British Rubi by mere collection and comparison of specimens. Might not something more be done by studying the effect on a few definite species of artificial change of environment, and of the results of crossing? If two small groups were studied in this way—say Mr. Roger’s swberectd and their hybrids with rZamat- Jolius, Selmert, macrophyllus, and corylifolius—might it not throw much light upon the whole genus, and beyond that? Short of that, might not much be done by studying the position in which definite species are growing with regard to “intermediates”? Is R. Rogersit =f. plicatus x carpinifolius? Does R, suberectus x corylifolius simu- late A. fissus ? Epw. G. GILBERT. Note on some vice-county records of Cornus suecica, Linn., etc.— To the list of Scottish vice-counties from which Cornus suecica has been recorded, given in Mr. G. G. Blackwood’s interesting note in the April number of the “Review” (p. 117), must be added 87 (So. Perth) and 111 (Orkney). In the former it has long been known to grow sparingly on Ben Ledi, where it was gathered by Professor J. H. Balfour and party on 21st July 1860, and in subse- quent years, as recorded in his “‘ Botanical Excursions,” pp. 309, etc. I have before me a specimen collected there so recently as July 1907. The Orkney record—from the island of Hoy—is given by Mr. Arthur Bennett in ‘‘ Ann. Scot. Nat. Hist.,” 1908, p. 251. To the English vice-counties should be added 59 So. Lancashire (7d., 2bid., 1911, Pp. 190). WILLIAM Evans. NOTES FROM CURRENT LITERATURE 185 Notes from Current Literature. Mr. E. S. Marshall (‘‘ Journal of Botany,” April 1912) in a short note records that Dr. Gliick, in examining the sheets of U¢ricularia in his herbarium, identified specimens as UW. ochroleuca R. Hartman from vice-counties 88, 98, 106, 108, and 112, as well as from Dorset v.c. 9. None of the Scottish specimens were true U. ¢ntlermedia. “South Kerry Plants,” by E. S. Marshall (‘Journal of Botany,” June 1912). In this Mr. Marshall gives valuable notes upon some of the Irish Saxifrages, and describes a new variety of S. hirsuza as var. acutidens. “Doux Labiées nouvelles pour la Provence,” by Alfred Reynier (“Bulletin de la Société Botanique de France,” 1911, No. 8). Contains lengthy notes on 4adlota nigra Linn., var. ruderalis, and Calamintha nepeta Savi, f. Gussonet. **Contribution a l’étude des Saxifrages du groupe des Dactyloides Tausch,” by M. D. Luizet (‘‘ Bulletin de la Société Botanique de France,” 1911, No. 8). ** Nagra olika typer af. Convadllaria majalis L.,” by Carl Skottsberg (“Svensk Botanisk Tidskrift,” Haft 4, p. 411). * Un Sagina nouveau présumé hybride: Saginza lemovicensis,” by FE. Simon. ? S. subulata x procumbens (“ Bulletin de la Société Bo- tanique de France,” 1911, p. xlii). *“Un Saule peu connu de la flore de France (Salix atrocinerea Brot.),” by Ph. Guinier (‘‘ Bulletin de la Société Botanique de France,” NQET, Pp. 1x). “The Grama Grasses: Boutelowua and Related Genera,” by David Griffiths (“‘Contributions from the United States National Herb- arium,” vol. xiv. part ili.). This is a paper of considerable value, containing good photographs and dissections of the various species described. “New or Noteworthy Plants from Columbia and _ Central America,” by H. Pittier. (‘Contributions from the United States National Herbarium,” vol. xiii. part xii.). A large number of the species described are trees, some of which are of considerable commercial value. “New or Interesting Mosses from Panama,” by R. S. Williams (“Contributions from the United States National Herbarium,” vol. XVi. part i.). “Contribution a l’étude des Muscinées de l’Ouest et du littoral,” by A. Coppey (“ Bulletin de la Société Botanique de France,” 1911, p- XX1). 186 THE SCOTTISH BOTANICAL REVIEW “On the Periodicity of the Phytoplankton of some British Lakes,” by W. andG. S. West (‘‘ Journal of the Linnean Society,” May 1912). ‘Notice sur les spores des Licheni blasteniaspori Mass,” by Abbé Hue (‘‘ Bulletin de la Société Botanique de France,” 1912, p. lxvii). “Notes Lichénologiques,” by M. Bouly de Lesdain (“ Bulletin de la Société Botanique de France,” 1911, No. 8). Contains descrip- tions of a number of new species. “On the Brown Seaweeds of the Salt-Marsh,” by Sarah M. Baker (“‘ Journal of the Linnean Society,” February 1912). endée considerée comme unité géographique et caracterisé “La Vendée consid t h t ctéris€e par sa flore,” by F. Hy (“Bulletin de la Société Botanique de France,” 1911, p. Xxvi). “The Relation of Ohio Bog Vegetation to the Chemical Nature of Peat Soils,” by Alfred Dachnowski (“ Bulletin Torrey Botanical Club,” vol. xxxix., No: 2), “An Ecological Study of a Cambridge Woodland,” by R. S. Adamson, M.A., B.Sc. (“ Journal of the Linnean Society,” February 1912). “Om en planmassig vaxtgeografisk undersékning of Sverige,” by H. Wilh. Arnell (‘‘Svensk Botanisk Tidskrift,” Haft 4, p. 418). “Observations on the Degree of Stomatal Movement in Certain Plants,” by B. E. Livingston and A. H. Estabrook (“ Bulletin Torrey Botanical Club,” January ig12). ‘“‘Researches on Heredity in Plants,” by Professor F. E. Weiss (“Memoirs and Proceedings of the Manchester Literary and Philosophical Society,” vol. lvi., part 1.). Reviews, Book Notices, ete. PRopRoMUS FLOR& BRITANNIC2. By FREDERIC N. WILLIAMS. Part IX., comprising the fourteen families in the four orders of Rhamnales, Gruinales, Hippocastanales, and Tricoccales. Pp. 477-532. Brentford: C. Stutter. March 1912. One year has elapsed since Mr. Williams published Part VIII. of his *Prodromus.” In this last part we have some interesting reflections on some British species. Of course, there are some name-changings and alterations; this seems to be inevitable in each succeeding publication. Whether we shall be plunged into as great a muddle as our American confreres, remains to be seen. It is not necessary here to enter into the scheme of arrangement— this has been ably commented on in the notices of earlier parts, 7.¢. REVIEWS, BOOK NOTICES, ETC, 187 by Mr. Hiern ;! so that the treatment of the species may be noticed, and especially of the varieties and forms, which it seems difficult to keep to any standard. For example, Cad/itriche, a genus very difficult to diagnose without fruit, has distributed among its species no less than twelve, exclusive of the normal forms. As one who has culti- vated these plants, I do not believe they will stand the test ; they are simply individual variation, ever reverting to their original type. Mr. Williams uses the genus /rangula Tour. for Rhamnus Frangula L. as & alnus Miller, giving reasons for so doing. For Linum perenne L. he uses Z. anglicum Miller; his reasoning here seems to lend itself to the alteration. For Z. angustifoum Huds. (1778) we have ZL. hispanicum Miller (1768). We are told that rodium ctcutarium Aiton has no varieties in Britain ; to this some will demur. In some cases the distribution given seems hardly full enough, ze. C. maritimum Aiton. In the genus Cadittriche we have C. platycarpa as a species apart from C. stagnalis, with five named varieties, etc., under them. Hegelmaier in his monograph? combined them, but he kept C. pedunculata DC. as a species. C. angustifolia Hoppe is kept as a species separated from C. intermedia Hoff. Certainly this has some characters that seem to commend this, but they require testing by cultivation, and the majority of Continental authors place it under C. verna L. seg. Under one of these he remarks (p. 509), ‘‘ The difference in form between the floating leaves and the lower leaves is very marked” ; but surely this is only a passing state. I believe it to be impossible to separate these plants by leaves alone, except in the second section (7.e. truncata and autumnalis). He keeps up C. pedunculata DC. as a species, and observes, “‘ It is interesting from the fact that it forms its fruit in early summer.” But this is simply because the water is evaporated earlier and the plants exposed to more sun, and within a few yards C. obtusangula Le Gall. (submerged) may be found in good fruit at the same time. C. verna he quotes as of Withering, ‘“‘ Bot. An. Veg. Brit.,” p. 2, 1776, as C. verna I.. has no meaning. But is Withering’s description (quoted) enough to determine this? C. autumnalis L. (October 1755) isreplaced by C. hermaphroditica, Juslenius, “Cent. Plant.” n. 89, p. 31 (February 1755), whose description consists of five words ; but I suppose Haller’s reference must be accepted. The distribution of this species is of interest in relation to C. truncata Guss. It extends from Shetland! south to Anglesea! and Cheshire! (53°°16 N. lat.), while ¢7wscafa extends north to Nottinghamshire at 53°26, so they slightly overlap. The record of “ Devon S.” in ‘ Topl. Botany” is probably an error, but it may have been /runcata not then separated in Britain. C. polymorpha Lonn. Mr. Williams passes with scant notice ; his 1 ** Jour. of Botany,” p. 229, 1909. 2 «Mon, Gatt, Callitriche,” 1864. 188 THE SCOTTISH BOTANICAL REVIEW observation on Lénnroth’s paper only refers to his “ Thesis, 1854,” but in the ‘“ Bot. Notiser” for 1867 he gives excellent drawings of all the Swedish species and amplifies the 1854 work. Under Polygala vulgaris L., var. grandiflora Bab., he remarks, “There are only two British specimens so named in the Herb. Mus. Brit.” But neither is Babington’s plant! or like it. The Faroe one also is not the variety. The Irish plant is certainly a variety, and Mr. Ball’s herbarium name of duscifolia well describes it; but this was occupied, and so Nyman, “ Consp. Fl. Europ.,” p. 83, 1878, named it P. Balti. Mr. Williams sinks all the plants called (in Britain) P. amara, P. amarella, P. uliginosa, and P. austriaca under P. amara L, (1759). Under Empetrum nigrum L. it might have been recorded that Boner found it in the Amberly Wildbrooks (Sussex) and Mitten in Dorset. Under the Box he does not refer toBabington’s note (“‘ Phytologist,” 21/1/1853) from Asser’s “ Life of King Alfred.” The remainder of this part includes five species of Luphorbia, and keeps up the original and suggestive ideas of former parts, though to some it may seem that the treatment of the species is unequal, especially as to distribution. THE SHINGLE BEacH aS A PLANT HasitatT. By F. W. OLIVER. (Plate IV. and Eight Figures in the Text.) “‘ New Phytologist,” vol. 'xi:, No; 3, March 1912: IN this interesting and instructive paper Professor Oliver gives the first instalment of what we hope may prove to be a monograph on the shingle beaches of this country, which he is studying from the point of view of their relations to plant habitat. After shortly discussing the origin of the four principal types of shingle beaches, viz. (1) the Fringing Beach, (2) the Shingle Spit, (3) the Shingle Bar, (4) Apposition Beaches, he proceeds to give an account of the shingle spit and its modifications. In this certain new facts and views of geological importance are set forth, such as can only be discussed fairly elsewhere; but atten- tion should be especially given to the following points. The spit is looked upon as having a phase of youth, under the organising in- fluence of the littoral current, when its growth is mainly in length, this being followed by a more or less prolonged phase of hook- formation—a phase of maturity—when the spit becomes subject to increasing tidal scour, which, in conjunction with heavy onshore gales, leads to the transfer of material and the production of a landward hook at its termination. Further, there may be reversions to the juvenile straight-growing phase, and alternations of such phases with those of maturity lead to spits having groups of hooks distri- buted along their length. The mobility of the shingle on shingle spits is shown to be due to (1) wave impact scattering stones over the crest, and, where more REVIEWS, BOOK NOTICES, ETC. 189 effective, leading to finger-like tongues of shingle to the rear of the spit, lying in the direction of principal wave impact. When high spring tides are accompanied by gales, the crest of the spit may be awash and the impact of the waves may then even promote a land- ward creep of the bank, the mobility of the bank being increased by supersaturation. (2) Percolation, in cases where the bank is steep-sided and the level of high tide above that of the salt-marsh enclosed by the spit. This leads to the erosion of ‘ravines” by landslip, and the formation of a terrace, by gravitation and detrital faces, on the landward side of the bank, the “ravines” being separ- ated by buttresses of shingle in a quiescent state. (3) Undercutting of the bank on the lee side by tidal or other currents, which some- times plays an important part in regulating the landward creep of the bank. Shingle beaches, and especially shingle spits, are shown to belie their appearance both in regard to the soil and to the water they contain. The supply of soil is derived from drift, that from the salt-marshes being considered of more importance than that from the sea, on account of its greater quantity, its richer manurial value, its frequent interstratification with the shingle on the lee side of the bank, and on account of its being the great agency by which certain seeds are sown and placed under favourable conditions for germina- tion. With this is contrasted the enduring sterility of the apposition type of shingle beaches, where contact with tidal waters is denied. The water of shingle banks is shown to be astonishingly copious and practically free from salt above the true salt-zone, and, moreover, suffers no diminution during periods of prolonged drought. The types of plant habitat on the shingle spit are classified as :— (1) The Sea Face, reached by ordinary tides and barren of vegetation. (2) Lhe Storm Shelf, with chiefly prostrate species of Asriplex and sometimes Leta maritima. (3) Zhe Crest, where wind exposure is a serious check to vegeta- tion, and sometimes distinguished as forming the last stronghold of plants endowed with the capacity of creeping up the shingle from the landward side. (4) The Back of the Bank, with its sheltered “ravines,” forming the chief region of vegetation, which shows indications of being separable into (1) a vegetation of dormant areas, and (2) that of areas in an unstable condition. (5) Zhe Terrace, the gathering-ground of escapes fromthe salt-marsh. (6) Zhe Hooks, which, apart from the terminal hook, are passive and consolidated, and may in certain cases yield distinctive plants as Lnula crithmoides or Limonium binervosum. In conclusion it may be said that the paper clearly demonstrates the close relation between ecological habitat and the effects of the geological factors of surface change in the shingle spit, and in its method and thoroughness forms an outstanding example of how ecological work should be prosecuted. 190 THE SCOTTISH BOTANICAL REVIEW A MONOGRAPH OF THE BRITISH DESMIDIACEZ. By W. and G. S. West. Vol. iv. Ray Society, London, rg12. Pp. xiv+1g91, Plates 96-128. Price 25s. net. WE are indeed glad to welcome the fourth volume of this masterly work, containing as it does the completion of the exceedingly difficult genus Cosmarium. No one who is not a student of this most complex subject can appreciate the amount of knowledge and labour required for the compilation of such a work, and the authors have conferred an incalculable benefit upon students by the undertaking. Besides the completion of the genus Cosmariwm, the genera Xanthidium and Arthrodesmus are dealt with, and the genus Staur- astrum started, the first forty-one species being described and figured. The authors describe three new species (as well as many varieties), viz. Xanthidium Orcadense, from a sphagnum bog in the Orkneys, and which the authors in 1896 described as X. Rodbinsonianum, from which it differs, however, ‘‘in its open sinus and in its more scattered and more reduced spines, and the rounded and less evident central protuberance”; Staurastrum fpilosellum, from Cornwall; and S, inflatum, from W. Yorks. The authors’ treatment of the genus S/aurastrum is worthy of note. Attempts to split the genus upon natural principles having failed, they group it in two divisions : Division I. Angles of semi-cells not produced into processes. Division II. Angles of semi-cells produced into processes. Each of these divisions, again, is divided into several sections. This treatment seems in every way satisfactory. As in former volumes, the book contains plates of all species and varieties described, while another valuable feature is an additional bibliography which brings the literature up to date. CLARE IsLAND Survey. Part XIV.: LicHENS. By Miss ANNIE Lorrain SmitH, F.L.S. Dublin: Hodges, Figgis & Co., 1911. Price 6d. Tue Report on the lichens of Clare Island made by Miss A. L. Smith is of very great interest, as itis the work of an accomplished lichenologist, who has quite recently completed the monograph of British lichens commenced by the Rev. J. M. Crombie. Miss Smith devotes six introductory pages to the geographical features of Clare Island and district, the rocks, and the ecological factors, which especially determine the distribution of these plants. The rocks are covered by grass, moor, and bog, but are often “‘ denuded of soil, and lie exposed to sun and wind—ideal situations for lichens.” In some parts rock specimens abound, being “of a more or less alpine character.” Quartzite, typically barren, here yielded AAzzocarpon veographicum, as elsewhere. Numerous corticolous species were found in the woodlands. Previous work in this district had been limited, and was mainly due to Larbalestier, who died only last year. REVIEWS, BOOK NOTICES, ETC. IOI But collections were made in 1909 and subsequently by Miss M. C. Knowles (Dublin), W. West (Bradford), W. A. Wattam (Huddersfield), and by Miss Smith and others. ‘The result was a collection of 280 species, of which only 30 are noted in Adams’ paper, for subprovince Co. Mayo, of which Clare Island forms a part. ‘Though some had been found in Galway, 30 to 40 are new to Ireland—a very good record. Nine noted by Adams were not seen, so that such species as Rocce/la fuciformis and Collema flaccidum may be extinct. Miss Smith remarks that Clare Island (and district) is specially favourable to lichens. An extremely interesting and graphic account, pleasantly written, is given of the occurrence of different dominant species. Inland Lectdea rivilosa forms patches 9 feet by 3 feet. It is noted that Parmelia saxatilis passes over to the allied species ?. omphalodes. Observations such as these show how indispensable field-work is to the interpretation of plant affinities and life-history. The luxuriance of lichen growth may be illustrated by the fact that a tree trunk was almost covered by Cod/ema nigrescens, a feature that here may be best paralleled in England in the South. Some rare species are recorded, e.g. Arthonia subvarians, etc. Miss Smith truly notes that the distribution of lichens is ecological even more than geographical. But it is clear that the geographical or physiographical conditions of the west coast of Ireland are primarily responsible for not only the wealth of moisture-loving cryptogams, but also for the characteristic phanerogams which are peculiar to this humid and warm region. In the enumeration of species the ecological distribution is given by denoting the habitat, tree or bark, rock and wall, ground and soil, by the letters B, R, and G. The list itself is of considerable interest and value, and is an important contribution to lichenological literature. A SHORT FLORA OF CAMBRIDGESHIRE, CHIEFLY FROM AN ECco- LOGICAL STANDPOINT. WITH A HIsToRY OF ITS CHIEF Botanists. By ARTHUR H. Evans and others (‘‘ Proceedings of the Cambridge Philosophical Society,” vol. xvi., part iil. ). ‘THis work has been written, as the author says, with the intention of bringing Babington’s work on the county up to date, and this it succeeds in doing excellently. The book is divided into four parts, viz.:—I., which gives a biographical sketch of the chief local botanists irom the time of Ray downward to present time; II., which deals with the physical features with its geological formations and attendent floras ; III., an annotated list of some of the rarer plants and extinct species ; IV., a general list of species with the numbers of the division in which found ; while V. deals with the Thallophyla. It is distinctly unfortunate that in the title there should be the somewhat startling announcement, “chiefly from an ecological standpoint,” as we find the only claim it can have to deal with ecology is that the county has been divided up into divisions follow- ing roughly certain “ geological formations.” We fear this scarcely VOL. I. 14 192 THE SCOTTISH BOTANICAL REVIEW justifies such a title ; indeed, it can be seen, from the district numbers placed after many plants, how little it tells of the ecology of any species. However this may be, the volume will be of great assistance to all field-workers in the county. The chapter upon the Characee, brought up to date by the Messrs Groves, is a very good example of the thorough manner in which these excellent workers carry out their investigations. The chapter on the Bryophyta is by the Rev. P. G. M. Rhodes, and the Alge by G. S. West, this latter being an extremely comprehensive and masterly study of the algal flora of the county. The final chapter, upon the Fungi, is by F. T. Brooks, and gives a list of the higher fungi recently found in the county. THE “WOODPECKER" Umbrella is the latest invention of the kind. It can be had at all prices from 10/6, for Lady or Gentleman. The ‘“WOODPECKER” Sunshade in any colour. TO BE HAD ONLY FROM THE PATENTEES JAS. ROBERTSON & SON, Umbrella Makers, 43 Queensferry Street, laypepners 30 & 32 Leith Street! : George Prescott & Go. (J. H. MURRAY), Specialists 52 QUEEN STREET, GLASGOW; | DUKE STREET, DUBLIN. Spectacle & Eyeglass Specialists. ooo The New Invisible Frameless Spectacles & Eyeglasses A Specialty. 100 Lothian Road, Edinburgh TELEPHONE—1478 Central. Glasgow—8630 City. Dublin—2279. Hours: 9-6.30. Please note Early closing Saturday 1.30. a S Vv Telegraphic Address: ‘LARCH,’ EDINBURGH. Telephone No. 2034. Now Ce Awarded 4 Gold and 4 Silver Medals at recent Flower Shows held in Edinburgh. ea) DAVID W. THOMSON Nurseryman and Seedsman 113 GEORGE STREET — EDINBURGH. —— Seed Warehouse—118 GEORGE STREET. Selected Vegetable and Flower Seeds, Bulbs and Forcing Plants, Retarded Bulbs and Plants, Garden Tools, Manures, &c. Catalogues Post Free on Application. NURSERIES—Granton Rd. and Boswall Rd. AN EXTENSIVE AND WELL-GROWN STOCK OF Forest Trees of all kinds, Ornamental Trees and Shrubs, Rhododendrons and Flowering Shrubs, Game Covert Plants, Fruit Trees, Roses and Climbing Plants, Herbaceous and Alpine Plants, ALL IN SPLENDID CONDITION FOR REMOVAL. INSPECTION INVITED. Catalogues Post Free on Application. vi iNT Contents PAGE THE GEOLOGICAL RELATIONS OF STABLE AND MIGRATORY Piant Formations. C. B. A MiB. €.M. ( Concluded) s : se CAITHNESS LICHENS. Rev. David Lillie, B.D. : 146 Linnzus’ “ FLtora ANGLICA.” G. ce Druce, M.A., Lalo a ; : 154 A New SprEcIES OF PYRENOCH#TA. Malcolm Wilson, DSc, F.LS. . ; : 161 AGATHOSMA TRICHOCARPA, N. SP. E. M. ie FLS. F.B.S.E. : ; . : : St KOZ THE Past History OF MONOCOTYLEDONS, WITH REMARKS ON THEIR ORIGIN. A. R. Horwood . ; sitet DOA RECENT ADDITIONS TO THE CAITHNESS FLoRA. Arthur Bennett, A.L.S. . : : ; : Sy ROT SHorT NOTEs :— Hierochloe odorata, Wahl. R. H. Corstorphine. » Etre oe Alchemilla acutidens, Buser. M‘Taggart Cowan, Jr. .. 183 Note on the Calluna-Mat Association of the Mountain Tops of the Northern Highlands. C. B, Crampton and M. Macgregor . : 4 rau ko British Rubi and environment, ate! E. G. Gilbert eS "| Cornus suecica, Linn. Wm. Evans ; 3 Ses tod NOTES FROM CURRENT LITERATURE Paes Reviews, Book NOTICES, ETC. :— Prodromus Flore Britannice. ¥F.N. Williams. Part IX. 186 The Shingle Beach as a Plant Habitat. F. W. Oliver. (“ New Phytologist,” No. 3, vol. xi.) : . 188 A Monograph of the British Desmidiacee. W. and G. S. West . ; = +. 4190 Clare Island Survey. Part XIV. : Lichens. Miss Annie Lorrain Smith : ee ge A Short Flora of Cambridgeshire. A. H. 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