I 



1907] CHRISTMAN—MORPHOLOGY OF THE RUSTS 93 



with the sporidia and ending with the fusion of two gametes, and 

 bearing asexually one kind of spores, the so-called spermatia. The 

 question as to how the so-called secondary aecidia arise must be 

 regarded as still unsettled. Dietel (ii) has shown that infections 

 from aecidia in the case of Uromyces scrophulariae DC. may repro- 

 duce crops of aecidiospores. In this case one or more of three things 

 may have taken place: the infecting aecidiospore may have germi- 

 nated by the formation of a sort of promycclium and sporidium, thus 

 returning to the uninucleated condition, as is the case in Endophyllum; 

 or these secondary aecidia may be borne upon a mycelium of binu- 

 cleated cells, in which case they are not aecidia at all, but rather 

 uredospores borne in rows such as occur in Coleosporium; or sper- 

 matia capable of producing infection may accompany some of these 

 forms having the secondary aecidia. 



Against this last view we have the present belief that the spermatia 

 are functionless, a belief which in view of the great number of forms 



( to be studied is certainly open to some question, especially since 



Brefeld (4) and Plowright (20) claim to have seen distinct evi- 

 dences of normal germination in the spermatia of Piiccinia graminis, 

 Uromyces pisi, Puccinia tragopogonis, Puccinia coronata, and others. 

 This is a behavior quite unlike what might be expected of true sper- 

 matia. In my opinion, the likeness of the rusts to the red algae is very 

 questionable, and the arguments that the spermatia are the former 



I incline rather to the view that 

 spermatia represent the once functional asexual spores of the game- 

 tophytc. This view finds support in the fact that they are in general 

 appearance very like the functional asexual spores (pycnidia) of the 

 gametophyte of certain ascomycetes; also in structure and general 

 appearance they are verj^ like the other gametophytic spores of the 



' rusts, the sporidia, which are still functional; further, unless we 



interpret the spermatia as the asexually produced gametophytic 

 spores, the gametophyte generation is left entirely without means of 

 reproducing itself without passing through the stages of the sporo- 

 phytic generation. As yet, however, it must be admitted that definite 

 evidence as to the nature of the spermatia is ver\' incomplete. 



The binucleated sporophytic generation which, as Maire (17) 

 has pointed out, is comparable to the generation with the double 



male 



ri 



1 



