HISTORY OF PLANTS. I/I 



lycopods), and also a plant of a size so large as to resemble a tree, 

 though in structure of so low a type as to belong to the algae (Nema- 

 tophyton). Other land plants were living also, but they were all of 

 a very low type. The land vegetation was marvellously different 

 from that of to-day, and we may almost look upon it as a flora of 

 marine algae which had been transferred to the land and then en- 

 larged. Still there was, even at this time, a differentiation into stem 

 and leaf, and this does not occur in ordinary algae. The Silurian 

 flora was in one marked respect very different from the Silurian 

 fauna. The latter has surprised us with its diversity and high 

 grade of development, while the former may equally surprise us with 

 its scarcity and its low grade. The development of plants had not 

 reached such a high state as the development of animals at this time. 



In the next age (Devonian) there was an undoubted advance. 

 Algae were still in abundance, as indeed they have been in all ages 

 up to the present time. But with the Devonian, undoubtedly, higher 

 plants appeared. True rhizocarps and lycopods (horse tails) were 

 abundant at this time, though possibly they may have begun in the 

 previous age. In the Devonian also we find true ferns, some of them 

 small and others of large size like our tree ferns. In this age, too, 

 appeared the first indication of the flowering plants in the form of 

 gymnosperms or conifers (yews and cordiates, an extinct family). 

 The flora of the Devonian was thus on the whole composed of the 

 highest of the cryptogams (lycopods) and the lowest of the phanero- 

 gams (evergreens and conifers). 



In the interval between the Devonian (3) and the Carboniferous (4) 

 ages there were great changes in the level of the land. After various 

 submergences it finally arose clothed with a flora of precisely the 

 same general character as that of the Devonian, but with new species 

 and genera. The changes had been sufficient to obliterate old and 

 produce new ones. The flora still consisted of the same groups of 

 plants with no advance in structure. The ferns became very diversi- 

 fied, and the horse tails and lycopods reached their greatest size, but 

 there was no advance in structure. The age was characterized, how- 

 ever, by the great development of the cone bearers (Gymnosperma), 

 ferns (Pteridophyta), and the horse-tail group (Lycopoda). The Car- 

 boniferous was an age of especially abundant vegetation, and to the 

 plant growth of that time we owe our beds of coal. 



Coming now into later periods, we find with the beginning of the 

 Mesozoic again a new flora, but again no advance in structure of much 



