ZOOLOGY AND BOTANY, MICROSCOPY, ETC. . 79 



afforded a safe anchorage to algae (and animals), which then began to 

 develop a multicellular structure and to elaborate modes of reproduction 

 and of spore-dispersal necessitated by their sedentary existence. After 

 further ages the sea-bottom gradually came right to the surface, and 

 the exposed algas and animals had to adapt themselves to aerial condi- 

 tions or to perish. Several of the best fitted successfully passed through 

 the ordeal, but in the struggle became so drastically altered, in shape, 

 structure, physiology and modes of reproduction that the ancestry of 

 the distinct phyla of the Bryophyta, Lycopods, Equisetaceae, Ferns, 

 Gymnosperms, x\ngiosperms, etc., is now untraceable, though in several 

 of them an ancient and primitive character survives in the structure of 

 the respective antherozoids, and affords powerful evidence as to ancestral 

 affinities. Another interesting group are the Fungi. These date from 

 the same period of land-emergence, and had a markedly polyphyletic 

 origin (e.g. Phycomycetes, Ascomycetes, Basidiomycetes, Uredineae) ; 

 they too came through great tribulation in adapting themselves to a 

 saprophytic or parasitic life and in elaborating resting-spores, air-borne 

 spores, etc., which enabled them to withstand drought and secure a 

 wide dispersal. No trace of the highly organized green algae of the 

 transmigration is to be found in geological strata. They became land- 

 plants, or they perished. But the brown and the red algae were not 

 fitted for the transmigration, being inadequately developed in reproduc- 

 tive mechanism (brown algae) or in vegetative structure (red algae). 



The memoir is of the highest importance in connexion with the 

 study of the fundamental facts of botany, and is replete with details, 

 deductions and arguments which can only be studied with advantage in 

 the original text. A. G. 



Terminology of Alternation of Generations in Plants. — D. Renxer 

 {Biol. CentralU., 1916, 36, 337-74 ; see also^o^. Centralhl, 1918, 137, 

 97-8). An attempt to bring uniformity into the terminology of alter- 

 nation of generations. The author disapproves of the term in the 

 Hofmeister sense, and seeks to prove among the most varied famihes of 

 the plant world that where alternation of phases is present, alternation 

 of generations does not necessarily exist also. " Alternation of genera- 

 tions" he acknowledges exclusively in tliose cases "where, over and 

 above the zygote, at least a second obligate germ-cell, a true spore, is 

 present, which does not originate directly at the germination of the 

 zygote." Under " generation " he understands a portion of the 

 development which is intercalated between two different obhgate germ- 

 cells, and to a certain extent exhibits vegetative growth. Alternation 

 of phases would then be an alternation of stages having haploid and 

 diploid nuclei and need not necessarily coincide with alternation of 

 generations. Thus Spirogyra, which completes its reduction-division on 

 the germination of the zygote, lacks, according to the author, an alter- 

 nation of generations. The author's view is that the gametophyte 

 begins with the gonospore, or in some cases with the gonotokont and 

 ends with the gametes, while the sporophyte represents a generation 

 which produces spores. The gametophyte is always haploid, while the 

 newly defined sporophyte is as a rule diploid ; but in those cases where 



