CHAPTER V. — COMPARATIVE REVIEW. — BAS1DI0MYCETES. 339 



of the comparison, are not more unlike the basidia of the Tremellineae than many of 

 these are unlike one another. The gelatinous character also of the membranes in 

 many Uredineae might also be mentioned, if such an argument were not too weak for 

 serious consideration. The statements made in former paragraphs show that the 

 teleutospores, or in some cases perhaps only the promycelia developed from them, in 

 the tremelloid Uredineae, are not only very like the basidia of the Tremellineae, but 

 strictly homologous with them. There is the same relation between the sporidia and 

 the basidiospores. 



Further there can be no doubt, according to the facts stated above on page 283, 

 that the teleutospores of the tremelloid Uredineae are strictly homologous phylo- 

 genetically with the teleutospores of the forms which produce aecidia, and that the 

 two sections together form the sharply defined group of the Uredineae. The rhythm 

 of the development in the species which form aecidia shows that this group belongs 

 to the series of the Ascomycetes (see page 132). The Basidiomycetes are thus 

 connected with the series of the Ascomycetes through the Tremellineae and the 

 tremelloid Uredineae. 



The teleutospores of the Uredineae, if referred to the general course of develop- 

 ment in the Ascomycetes, come under the definition of gonidia, and the basidiospores 

 of the Basidiomycetes, which are phylogenetically homologous with them, necessarily 

 come under the same idea. If those members of the development are said to be 

 homologous which occupy corresponding places in the course of the ontogenetic 

 development, the homology between the series of the Ascomycetes and the 

 tremelloid Uredineae and Hymenomycetes is interrupted and not restored in the sense 

 explained on page 123. 



And now if in deciding with regard to the phenomena of relationship which arise 

 out of the similarity of the development we hold to the view that the forms in question 

 are all phylogenetically connected, the question arises, whether in passing from the 

 tremelloid Uredineae and Basidiomycetes to the Uredineae with aecidia we should 

 suppose that the latter proceeded from the tremelloid Uredineae or Basidiomycetes 

 and therefore acquired the sporocarp as a new member of the development which was 

 wanting in the earlier series ; or whether the converse is not the more probable course 

 of the phylogenetic development, and the sporocarp known as the aecidium has been 

 ejected from the ontogenetic development of the tremelloid Uredineae and Basidio- 

 mycetes. One of the two things must obviously have taken place. In the first case the 

 phylogenetic formation of the Uredineae bearing aecidia would be an act of progressive 

 development, for a new and highly differentiated member would be added to those 

 previously existing in the development : in the other case the development would be 

 retrogressive, since this section of it would have disappeared. It was remarked above 

 on page 285 and on a former occasion ' that the absence of every kind of intermediate 

 form is opposed in this case to the theory of a progressive development ; there would 

 be a jump) from the tremelloid Uredineae to the perfect species with aecidia, and we 

 must put up with it if it cannot be avoided, but our experience of known cases of 

 progressive development does not add to its plausibility. On the other hand, there 



1 Bot. Ztg. 1879, p. 825. 

 z 2 



