98 



HARDWICKE'S SCIENCE-GOSSIP. 



of modern type to which it is comparable. The 

 primary structure consists oflarge tubular cells without 

 apparent termination, and devoid of structural mark- 

 ings. The loose character of the entire structure, the 

 interminable cells, their interlacing, and finally their 

 branching into a secondary series of smaller filaments, 

 point with considerable force to the true relationship of 

 the stem, as being with Algce or other Thallogens." 

 Sir J. W. Dawson adds : " When we consider that 

 Nematophyton was a large tree, sometimes attaining 

 a diameter of two feet, and a stature of at least twenty 

 before branching ; that it had great roots, and gave 

 off large branches, and that it was an aerial plant, 

 probably flourishing in swampy flats ; that its seeds 

 are so large and complex, as hardly to be regarded as 

 mere spores, we have evidence that there were, in 

 this early Paleozoic period, plants scarcely dreamt of 

 by modern botany." 



Many other fossil impressions, some of doubtful 

 origin, some of genuine Algae, have been found 

 belonging to this period, showing that the old 

 Cambrian and Silurian seas were tenanted by sea- 

 weeds not very dissimilar to those of the present 

 time ; also we have traces of primaeval Rhizocarps 

 and Lycopods, which can be better treated of in 

 describing the vegetation of the succeeding Devonian 

 age. 



In the Devonian age, or as Sir J. W. Dawson 

 prefers to call it the Erian, great geological changes 

 took place ; vast foldings of the crust of the earth, and 

 emissions of volcanic rock. In North America " while 

 at one time, the whole interior area of the continent, 

 as far north as the Great Lakes, was occupied by a 

 vast inland sea studded with coral islands, the long 

 Appalachian ridge and the old Laurentian land began 

 later on to assume something of the form of the present 

 continent. The America of this Erian age con- 

 sisted during the greater part of the period of a more 

 or less extensive belt of land in the north, with two 

 long tongues descending from it, one along the Appa- 

 lachian ridge in the east, and the other in the region 

 west of what are now the Rocky Mountains. On the 

 sea-ward sides of these there were low lands covered 

 with vegetation ; while on the inland side, the great 

 interior sea, with its verdant and wooded islands, 

 realised, though probably with shallower water, the 

 condition of the modern Archipelagoes of the Pacific. 

 The climate was mild, and admirably suited to 

 nourish a luxuriant vegetation. New forms of plants 

 seem to have been introduced from the North, where 

 the long continuance of summer sunlight, along with 

 great warmth, seem to have aided their early 

 development and extension." 



In Europe the conditions were somewhat similar, 

 having in the earlier portions "great sea areas with 

 insular patches of land, and later on>wide tracks of 

 shallow and partly enclosed water areas, swarming 

 with fishes, and having an abundant vegetation on 

 their shores." The Old Red Sandstone of Scotland, 



with its strange mailed and plated fishes, represents 

 the former state of things ; and the Devonian of 

 England, the time of rapidly shallowing seas. The 

 vegetation of this period bore a strong resemblance 

 to that of the coal forests, though all the species were 

 different. Ferns flourished with the utmost luxuri- 

 ance, the oldest yet known being found in the Middle 

 Erian. Some of these attained the dimensions of 

 tree-ferns, and in the Upper Devonian of Gilboa, New 

 York, the remains have been found of a forest '^of 

 tree-ferns standing in situ with their great mass of 

 aerial roots attached to the soil in which they grew. 

 These aerial roots introduce us " to a new contrivance 

 for strengthening the stems of plants by sending out 

 into the soil multitudes of cord-like cylindrical roots 

 from various heights on the stem, and which form a 

 series of stays like the cordage of a ship. This method 

 of support still continues in the modem tree-ferns of 

 the tropics." But other tree-ferns of this age show 

 near approaches to the mode of development of 

 exogenous stems, and for a proper description of the 

 modifications of these transitionary stems, we must 

 wait for an evolutionary botanist. Two types of 

 Gymnosperms (pines and yews) now make their 

 appearance ; the Taxineae or yews, and an extinct 

 family, the Cordaites, with leaves like those of broad- 

 leaved grasses or irises. The yews, though belonging 

 to the so-called "naked seeded" plants, protect 

 their seeds by a succulent cup-like receptacle, out- 

 wardly resembling a true berry. No fruit has how- 

 ever as yet been found of these Erian Taxinere, and 

 it is doubtful if even the leaf is known. Leaves 

 possibly belonging to them, resemble the modern 

 Gingko of China. The Taxinese are chiefly known 

 by their mineralised trunks, which are "often found, 

 like drift-wood on modern sandbanks, in the Erian 

 sandstones and limestones. They often show their 

 structure in the most perfect manner in specimens 

 penetrated by calcite or silica, and in which the 

 original woody matter has been changed into anthra- 

 cite and even graphite. These trees have true woody 

 tissues, with that beautiful arrangement of pores or 

 thin parts enclosed in cup-like discs, characteristic of 

 the coniferous trees." They flourished, to all appear- 

 ance, simultaneously in various parts of Germany, 

 Scotland, and America. Indeed one realises in 

 reading of the progress of plant life through all 

 geological time up to the glacial period, that the 

 northern parts of Europe, Asia, and America, con- 

 stituted one vast continent, where plants, possibly 

 originating in those regions now occupied only by 

 thick-ribbed ice, spread south and east. The heat of 

 the entire year, the long summer sunlight, the complete 

 rest of the dark season, all seem to have contributed to 

 make the Arctic regions of the earth (notably Green- 

 land), a most successful hot-house for plants, and 

 there we have every reason to suppose the highest of 

 all plants, the deciduous exogens, were first developed. 

 In marshy places in England still grow curious 



