UREDINALES 587 



Their point of view rests mainly on structure of the male sexual organ, 

 which has survived as the pycnium. This appears very similar to the 

 " spermogonium" of the Ascomycetes, e.g., Poly stigma; furthermore, the 

 formation of a sweet solution and the odor which is detectible by man 

 may be considered as entomophily. Thus the pycnospores correspond 

 extensively in form and size to the spermatia of the lichens, they possess, 

 as these, large nuclei and very small amounts of cytoplasm and reserve 

 materials. Also, up to the present, they have not been germinated at 

 least to the stage of infection of the host. 



The survival of the corresponding female organs would then be sought 

 in the aecia. The ascomycetous ancestors had simple unicellular 

 oogonia with unicellular trichogynes. The oogonia were joined together 

 in groups and were fertilized by the spermatia arising in the spermato- 

 gonia. During the degeneration of sexuality, the spermatial fertiliza- 

 tion disappeared and in its place two female oogonia copulated with 

 each other. The survivors of these gametangia are the present palisade 

 cells which may be regarded as a sorus of reduced female organs. The 

 survivors of the trichogynes remain as sterile cells cut off at the top of the 

 palisade cells; they have lost their function and have become buffer cells 

 whose function is passive, i.e., their dissolution gives the space necessary 

 for the development of the spores. 



Mme. Moreau (1914) has sought for a different significance for the 

 aecia. She proceeds from the hypothesis of Dangeard of gametophores 

 in the Ascomycetes. The present aecia were preceded by pre-aecia in 

 which chains of female gametes ("pre-aecidiospores") were formed upon 

 the basal cells ("gametophores"). Likewise, a series of male sexual cells 

 were cut off in the pycnia. The male and female sexual cells passed into 

 the open and copulated. Because of the degeneration of sexuality, the 

 plasmogamy followed within the female gametophoric sori between two 

 female gametes. The differentiation of gametes undergoes no interrup- 

 tion from this, only they are henceforth binucleate, behave no longer as 

 gametes but divide into aeciospore and stipe cell. 



These conceptions (assuming that the phragmobasidium is originally a 

 form of basidium) offer the advantage that they create in the Uredinales 

 the sought-for link between the Ascomycetes and the Basidiomycetes; 

 the latter had developed from the former through the rust series to the 

 saprophytic forms. Other explanations, however, are possible. Thus, 

 it is questionable whether the pycniospores are functionless spermatia, 

 and accordingly under all conditions incapable of infection, since they 

 are usually regularly and completely formed, even when in the micro- 

 forms the other functional spore forms are suppressed. Here it is reason- 

 able to suppose that for their further development they need the action 

 of digestive juices of animals (Jaczewski, 1910). Even if they were func- 

 tionless one could say more simply, that as diploconidia (urediniospores) 



