322 SCIENCE PROGRESS. 



differentiation of the moss-plant into axis and leaf, and by 

 the view that sexuality must be associated with the more 

 highly developed generation, the attempt is made to derive 

 the fern-plant from the moss-plant alone, the sporogonium 

 having no equivalent in the life history of the fern. This 

 view lost sight of the homologies already recognised by 

 Hofmeister throughout archegoniate plants. While the 

 general statement, that the two generations in these plants 

 arose by individualisation of parts of a single generation, 

 appears to be in agreement with the antithetic theory, which 

 has next to be discussed, the application of the view made 

 in the comparison of Moss and Fern shows that it is 

 essentially different. 



The series of papers by Celakovsky and Pringsheim 

 which have now to be mentioned are of special importance, 

 since the problem of the nature of alternation in the arche- 

 goniatae assumes in them the form which in the main holds 

 at the present time. An important character, distinguish- 

 ing these works from nearly all those previously referred to, 

 is that alternation of generations in plants is considered by 

 itself, no attempt being made to fit the phenomena into a 

 classification of the analogous occurrences in animals. In a 

 paper published in 1868, 1 Celakovsky recognises the work 

 of Hofmeister and Pringsheim on the life histories of Algae 

 and Archegoniatae as the basis for a consideration of the 

 vegetable kingdom as a developmental whole. The sexual 

 generation which is alone represented in most Algae is 

 termed the Protophyt, while the succeeding generation 

 which produces reproductive cells asexually is the Antiphyt. 

 This "polar alternation of generations" is distinguished 

 from other subordinate forms. Among the Algae it is 

 found in (Edogonium and Coleochcete. In a subsequent 

 paper- these views are elaborated, and a general survey 

 taken of the phenomena included under the term alternation 

 of generations. In accordance with the views of Braun, 

 but in opposition to those already expressed by Sachs, 3 the 

 shoot is recognised as the simplest vegetable individual, and 



Celakovsky ( 1 ). ^ Ibid. {2). 3 Sachs. 



