BOTANY 



sperms for palaeozoic fern-like plants bearing seeds. 

 Subsequent studies, notably by Professor Oliver 

 and his pupils, have shown that nearly all the 

 supposed ferns of that period really bore seeds of a 

 variety of types, the detailed anatomical investigation 

 of which has thrown a flood of light on these early 

 stages in the evolution of the seed. Although 

 much yet remains to be done, this important 

 chapter in the history of paleobotany has shown 

 that terrestrial plants responded to the need, or at 

 any rate benefited from the advantages of protection 

 of their embryos by developing various types of 

 seed-structures at a very remote period. 



A still more recent development in the study 

 of fossil plants, and one which is perhaps of even 

 wider significance, is in relation to the still more 

 ancient Devonian flora. Important as is the 

 development of the seed habit, the transitional 

 stages by which Alga? gave rise to land-plants is 

 an even more informing chapter in evolution. 

 How sea-weeds, living in a dense water-medium 

 and relying partly upon buoyancy, requiring little 

 differentiation of tissue to give them rigidity or 

 for purposes of conduction (since their nourish- 

 ment could be absorbed at any point), and show- 

 ing relatively little differentiation in the functions 

 of parts, could develop into land-organisms with 

 roots in the soil, more or less rigid stems to hold 

 them upright against the stresses of an aerial 



l S7 



