60 THE JOURNAL OF BOTANY 



into being and elaborated those morphological and anatomical cha- 

 racters which we find in marine algse of the present time — e. g., 

 filamentous or parenchymatous fronds, all sorts of ramification, leaf- 

 like ramuli, shrubby habit, apical and meristematic growth, haptera, 

 mucilage hairs, reproductive organs in great variety, alternating 

 generations, sporangia, &c. — in fact, all the normal equipment of 

 marine phytobenthon. After further ages the sea -bottom graduall}- 

 came right up to the surface, exposing whole continents of benthic 

 life to the severe ordeal of an aerial environment. Thus began 

 the Epoch of the Land Flora ; and any algse that failed to adapt 

 themselves to the novel and exacting conditions perished miserably. 

 The severity of the struggle was mercifully tempered by the 

 exceeding slowness of the changes by the daily tides, and by 

 the newly acquired advantages of a vastly increased supply of sun- 

 shine and oxygen. The chief problems to be met Avere the risk of 

 desiccation, the loss of food-salts, the need of a sti:ffening endo- 

 skeleton, as well as the adaptation of the organs and modes of 

 reproduction to meet the requirements of the new aerial conditions, 

 and the modification of the spore-mechanism to secure aerial dispersal. 

 Dr. Church has much to tell us about these matters — such as the 

 production of roots, the origin of the transpiration current and of 

 stomata, the polyphyletic elaboration of that successful adaptation 

 the archegonium,' the"^ apparent decadence but really efficient economy 

 of the gametophyte, the spore- wastage of the Fern, heterospory, &c. 



It was the Green Algse only that succeeded in gaining a footing 

 on the dry land, and of these only the highest "types survived ; hut so 

 completelV altered have they become in shape, structure, physiology, 

 and reproduction, that their algal ancestry is now untraceable. We 

 have distinct phyla of Bryophyta, Lycopods, Equisetaceai, Ferns, 

 Gymnosperms, Angiosperms, &c. (The antherozoids of the Lycopods 

 and Ferns indicatethat the cleavage between these two ph^da reaches 

 back to the Planltton Epoch.) Two other interesting groups that 

 date from the same period of land-emergence are the Characese and 

 the Fungi. To the latter a long and instructive chapter is devoted 

 pointing out their markedly polyphyletic origin {e. g. Phycomycetes, 

 Ascomycetes, Basidiomycetes, Uredinese) from algae which held their 

 own by reason of adopting a saprophytic or parasitic life, and by 

 elaborating resting-spores, air-borne spores, &c., which withstand 

 drought and ensure a wide dispersal. No trace of the highly 

 organized green alg* of the transmigration is ever likely to be 

 found in geologic strata, since they were earlier than the sedimentary 

 rocks. They developed into land-plants and left no trace in the 

 ocean. Brown and Red Algse, however, were unfitted to benefit 

 bv the transmigration, the brown being inadequately developed in 

 reproductive mechanism, the red in vegetative structure. They are 

 with us still and are little altered. That the transmigrant land-fiora 

 should seem so unconformable with modern marine algse is no more 

 surprising than that the land-mammals are unlike the fish. 



The above sketch briefly indicates the scope and importance of 

 Dr. Church's meinoir and the originality of his views. No such 

 clear- sio-hted and thoughtful contribution to the study of plant- 



