CHAP, i The Nature of Alternation of Generations 49 



alternations in the Archegoniatae, as he attributes to the 

 seaweeds mentioned the possession of three generations. 



A few years later, as knowledge of life- histories of various 

 forms increased, the subject again attracted a great deal 

 of attention and controversy became keen. A. Braun made 

 a contribution to the discussion in 1875, but though he 

 took a wider and more philosophical view than his pre- 

 decessors, examining anew the possible correspondence of 

 the alternation with similar phenomena in the animal 

 world, he did not make matters clearer, or bring to light 

 new facts. On the whole his reasoning agreed with that 

 of Celakowsky, but he introduced a new factor into the 

 problem by directing attention to the importance of taking 

 into account considerations of phylogeny. He definitely 

 stated the opinion that the sporophyte is a later genera- 

 tion than the gametophyte. 



In the first edition of his Lehrbuch, Sachs treated of the 

 subject with a certain caution, though he supported on 

 the whole the views held by Celakowsky. He held that 

 the essential condition for the passage from one alternate 

 generation to the other is a change in the law of growth, 

 though he admitted that it bears an intimate relation to 

 the production of sexual and asexual cells. In 1874, how- 

 ever, he took up a much stronger attitude. He added 

 many other plants to Oedogonium and Coleochaete as 

 exhibiting an alternation similar to that in the Mosses and 

 Vascular Cryptogams, specifying Mucor, Penicillium, and 

 other fungi, and the majority of the group he called the 

 Carposporeae, including here both the Ascomycetes and 

 the Rhodophyceae. In the latter group, then generally 

 called the Florideae, he said that there is a true alternation 

 of generations which may be considered rudimentary or fully 

 developed, according as the structure of the sporocarp is 

 simpler or more complicated in the latter case he held it to 

 constitute an alternating generation comparable with that of 



GREEN D 



