588 COMPARATIVE MORPHOLOGY OF FUNGI 



multiplied, the haploconidia became insignificant, except in Gallowaya, 

 where they are vestigial although the haplont is dominant. If the pycno- 

 spores were spermatia it would be inconceivable why they should arise 

 principally on the upper side of the leaf while the aecia which they should 

 fertilize arise on the lower side, or that, e.g., in Cronartium ribicola, they 

 precede the aecia by at least one year (Colley, 1918; Adams, 1921). 

 Furthermore in the Ascomycetes the functionless male sexual organs dis- 

 appear before the female, hence it would be difficult to understand why 

 their descendants would be unaltered and still form male sexual cells, 

 capable of "germination'' to a limited degree, while the female sexual 

 organs, which continue to fulfill their function, are deformed beyond 

 recognition. Furthermore in the development of the aecia, the 

 homologizing of the sterile cells at the top of the palisade with the 

 trichogyne, is not satisfactory. 



Further, certain theoretical considerations contradict the direct 

 derivation of the Uredinales from the Ascomycetes. In the ancestors 

 among the Ascomycetes, it must have been a question of very primi- 

 tive forms, e.g., Silurian, in which the ascus was eight spored and still 

 plastic. From this, in the course of time, the phragmobasidium of 

 the Uredinales at present has developed so far that none of its variants 

 may be referred to the ascus as an ancestral form. Vice versa, one 

 must assume that the sexual organs which early became functionless 

 were able to hold their own during this long course of develop- 

 ment and even, in certain cases, to form sexual cells still capable of 

 "germination." Such a conception is fundamentally improbable, for 

 it is shown in all series of the Ascomycetes, particularly, that the sexual 

 organs are especially liable to reduction, gradually become modified, 

 degenerate and disappear entirely. In these changing forms, however, 

 the gonotoconts, the asci, remain constant. From the Protascineae 

 up to the highest Euascomycetes, they remain essentially the same in 

 form and biological value, thus characterizing the Ascomycetes as a 

 homogeneous group. If, however, one wishes to derive the Uredinales 

 directly from the Ascomycetes, their development must have proceeded 

 in the opposite manner. If the otherwise stable ascus has changed 

 directly into a conidiophore, which does not resemble it even in spore 

 number, while the otherwise variable sexual organs retained their ability 

 to function and even to form sexual cells capable of germination, it is 

 the first example of such an interchange in the phylogenetic law of con- 

 tinuity. This direct derivation of the Uredinales from the Ascomycetes, 

 as significant as it was in its time, finds no support today. 



B. O. Dodge (1924, 1925, 1926) develops an interesting modification 

 of the hypothesis of the relationship of the Basidiomycetes to the red 

 algae, which meets most of the objections raised against that hypothesis. 

 Just as the Ascomycetous line is characterized by the gradual degenera- 



