54 Morphology BOOK i 



to cover also the gametophytes and sporophytes of the 

 highest as well as of the lowliest plants. 



A reply to Pringsheim was made by Celakowsky in the 

 following year. In this he set himself to combat again the 

 central position of his opponent by showing how the new 

 discoveries were easily reconcilable with his own views. 

 He pointed out that the normal sequence of alternation is 

 not lost in the occurrence of apogamy and apospory, but 

 that all that happens is the omission of a particular stage. 

 His explanation of the two phenomena seems a little forced ; 

 he claimed that apospory is explicable if we admit the 

 origin of all the vegetative cells of the sporophyte from 

 primitively reproductive cells, and that apogamy proves 

 nothing further than that the sporophyte can arise from an 

 indifferent cell of the prothallus instead of from a special 

 sexual cell by a sexual process. 



Celakowsky found himself partially in accord with Pring- 

 sheim on the position in the cycle of the cystocarp of the 

 Florideae and the sporocarp of Coleochaete. He conceded 

 that the former need not be regarded as a definite genera- 

 tion, but he laid much stress on the similarity of Coleochaete 

 with the liverwort Riccia. The sporocarp of Coleochaete 

 is so far homogeneous that all its cells produce spores, 

 while the sporogonium of Riccia shows so much differentia- 

 tion as to have the sporogenous cells covered in by a pro- 

 tecting layer or membrane. The difference between the 

 two is really the sterilization of certain cells of an originally 

 sporogenous body. As we shall see later, this forms the 

 starting-point of a theory of the sporophyte elaborated 

 subsequently by Bower. 



A new feature was added to the controversy by Cela- 

 kowsky's suggestion that the sporogonium in the Muscineae 

 is not only antithetic to the gametophyte in completing 

 the life-cycle, but is a third newly-arrived generation inter- 

 polated between the sexual and the first neutral or asexual 



