November. 1911. 



KNOWLEDGE. 



439 



ice reached the Bristol Channel, in big glaciers like those of 

 the Antarctic or Greenland. The glaciation in Ireland was 

 even more extreme, for no part escaped — even the warmest 

 parts of the south-west are striated and covered by moraine 

 material, the ice forming bergs so large that they floated to the 

 Scilly Isles before melting. Obviously, no temperate plant 

 could survive such conditions, and even if we consider the 

 non -glaciated area south of the Severn and Thames, we find 

 evidence of such cold as precludes the possibility of warm 

 nooks in which the temperate flora may have survived. 



If the southern plants were completely swept away by the 

 cold, how did they come back again, especially to islands like 

 Ireland and the Scilly Isles, and how did they obtain their 

 present singular distribution ? Before we adopt the view that 

 for plants to spread to islands one must have land connection 

 — Britain has often been connected with the Continent — one 

 must remember the rapidity with which the exterminated flora 

 of Krakatoa came back. Moreover, some peculiarities in our 

 flora cannot be explained by land connection ; for instance, 

 the Pyrenean element in our flora is practically confined to 

 Cornwall and the West of Ireland, but geologists nowadays 

 will not agree to the reconstruction of a lost Atlantis to 

 account for this pecuhar distribution, since no likely elevation 

 of the land would suffice to connect the areas mentioned. 



Chance introductions of seeds during thousands of years 

 explain the existing peculiarities of geographical distribution 

 in a way that no changes of sea or land or climate will do. 

 Our alpine flora consists largely of survivors from a colder 

 period ; but the rest of our flora is constantly being added to 

 by chance introductions from the nearest continental shore — 

 hence the .Atlantic element and the Eastern element, though 

 not consisting to any great extent of maritime plants, are con- 

 fined mainly in Britain to areas within a few miles of the 

 coast. Seeds are evidently brought from the Continent and 

 scattered broadcast over certain coastal districts, and they 

 grow and spread where soil and climate are suitable ; but the 

 post-Glacial period has been so short that the process is still 

 incomplete, and the slow spreading inland has only as yet 

 extended a few miles. 



-Mr. Keid concluded by stating his view that there is no such 

 thing as a native plant in Britain. Our flora has been swept 

 away like that of Krakatoa, but we have arrived at a nnich 

 later stage in the re-peopling of our islands. ''It seems to me 

 far more interesting to watch this process of introduction, 

 change and spreading, than to enter into speculations as to 

 what species shall be listed as 'natives,' 'denizens,' or 

 'colonists.' No such differences exist ; it is all a question of 

 degree. Britain for several thousand years has been receiving 

 colonists from all sources, and the process still goes on. The 

 oldest element in our flora — the alpine — occurs on nearly all 

 our mountains ; for it once occupied the intervening areas, 

 and it does not greatly depend on conditions of soil. The 

 limestone, aquatic, and Lusitanian flora, on the other hand, 

 are more recent introductions ; they can never have occupied 

 continuous areas, and their present distribution is full of 

 singular anomalies. These three elements of our flora are 

 steadily growing in importance, while the alpine element is 

 stationary or tends to die out." 



PAPERS ON PALAEOBOTANV.— Palaeobotany was 

 well to the fore, figuring largely not only in the Presidential 

 .Address to the Section but also in the papers read. 



In a paper entitled " A Palaeozoic Fern and its Relation- 

 ships " (not actually read, owing to lack of time), Dr. D. H. 

 Scott described a specimen of one of the simpler Palaeozoic 

 Ferns (Primofilices of Arber, Coenopterideae of Seward), 

 probably a new species of Zygoptcris [Z. Sutcliffii). The 

 stem of this new specimen has a five-rayed star-shaped stele, 

 leaf-trace bundles with axillary shoots, scale-leaves (aphlebiael, 

 and adventitious roots ; the characteristic internal xylem, 

 consisting of narrow tracheids embedded in parenchyma, is 

 especially well shown both in the main stem and in the 

 axillary stele. The leaf-trace is crescentic in section ; the 

 evidence of the new specimen favours the view that the large 

 strand given oft' from the stele is really a leaf-trace .and not 



itself a branch — the branch which the leaf-trace gives off 

 higher up may therefore retain the name "axillary shoot" 

 originally given it by Stenzel ; the course of the aphlebia- 

 strands, given off by the leaf-traces both before and after their 

 separation from the stele, could be clearlv followed. 



Dr. Benson described " The Structure of a New Type of 

 Synangium from the Calciferous Sandstor.e Beds of Pettycur, 

 Fife, and its Bearing on the Origin of the Seed." This 

 synangium, or chambered spore-case, is attributed to the 

 Pteridosperm Hcterangiiim gricvii, and probably represents 

 the pollen synangium of that plant. It differs from all 

 hitherto described synangia in the variety and large proportion 

 of its sterile tissue, which shows the sclerotic plates 

 characteristic of the inner cortex of Heferaiigiitin grievii. 



Numerous vascular bundles with hydathodal (water-gland- 

 like) ends occur, and irregular longitudinal dehiscence was 

 brought about by the swelling of hygroscopic fibres. Another 

 wholly new feature is the occurrence of both central and 

 peripheral loculi (four central and twelve peripheral). The 

 loculi agree in size and form with those of the incrustation 

 fossil, Diplotheca stcUata (Kidston), which is identified as 

 the same synangium in a dehisced phase. The discovery of 

 the structure of this early synangium adds fresh confirmation 

 to the synangial theory of the seed, which may be restated as 

 follows : The Palaeozoic ovule of the Lagenostoma type may 

 be regarded as the product of the elaboration of a synangium 

 comparable to the above — the megaspore or embryo sac being 

 derived from the central group of loculi, and the canopy and 

 peripheral part of the ovule from the peripheral part of the 

 synangium with its envelope, twelve loculi, cortical tissue, and 

 vascular bundles. 



Professor Seward read a preliminary account of his observa- 

 tions on a petrified Jurassic plant from Scotland, resembling 

 Bcniicttitcs in some respects, but showing peculiar characters 

 of its own, such as the presence of large quantities of fila- 

 mentous hairs forming a packing between the bracts of the 

 cone. 



Mr. H. H. Thomas described some " Recent Researches of 

 the Jurassic Plants of Yorkshire," from which it appears 

 probable that some extremely interesting results may be 

 expected. The paper gives a summary of some results already 

 obtained by Nathorst, Halle and the writer. For instance, 

 from material collected on the Yorkshire coast, Nathorst has 

 recently discovered the male sporophylls of Willianisonia. 

 which are joined into a cup-like structure somewhat comparable 

 to a flower, and are covered with large sessile synangia from 

 which the remains of the microspores (pollen-grainsi can be 

 extracted by treatment with acid ; the female cone of 

 Willianisonia closely resembles that in Bcniicttitcs. but 

 the flowers were unisexual. Thomas recently found a new 

 Bennettitalian flower which appears to be bisexual, like the 

 American specimens of Bciincttitcs (Cycadcoidca) ; the 

 central axis bore the usual ovules and intraseminal scales, and 

 below this there was a whorl of five or six large free sporophylls 

 arranged like the petals of a hypogynous flower, each bearing 

 five or six large kidney-shaped sporangia. Reference was 

 also made to the discovery of small fruit-like bodies named by 

 Mr. Thomas as Cay ton ia ; they appear to contain the remains 

 of about ten seeds, and similar isolated seeds have been found, 

 some of the structure being preserved — e.g., integuments, 

 micropylar tubes, and nucellus. Among various interesting 

 Ferns there are forms allied to such modern genera as Todca. 

 Cyathea, and Marsilia. 



In a short paper. Miss Lockhart made a "Contribution to 

 the Theory of the Formation of Calcareous Nodules containing 

 Plant Remains." Three boulders from the Calciferous Sand- 

 stone of Pettycur were entirely cut into thin serial sections in 

 the search for a minute object, and it was thus possible to 

 trace the position, in a block, of any particular plant. 

 Metaclcpsydropsis duplex and Botryopteris antiqna were 

 chosen, as they presented a contrast between a large and a 

 small plant. The clear delimitation of even the smallest frag- 

 ments points to mechanical fracture subsequent to inunersion, 

 and the parallel position of plant remains in the boulder further 

 indicates the agency of water currents. The results confirm 



