82 BOTANICAL GAZETTE [august 



plete life-cycle of a form like Phragmidium violaceum with that of 

 Phragmidium potentillae canadensis^ in which the aecidium is lacking, 

 the question at once arises whether forms with a less number of spore 

 types are to be considered as primitive and incomplete and in the 

 process of developing into the conditions in Eupuccinia, or whether 

 they are reduced and degenerate types. This question can be settled 

 only on the basis of a complete morphological analysis of all the 

 spore forms in question, and the following studies were undertaken 

 as a contribution toward this end. 



The most varied morphological interpretations have been given 

 for each of the spore forms of the rusts, and it is worth while to sum- 

 marize briefly the literature from this standpoint- 



DeBary^s (id) interpretation of the relations of the spore forms, 

 given more than twenty years ago, has been recognized by many 

 even to the present day as authoritative. He says: ^'The develop- 

 ment of the aecidium-forming Uredineae agrees so nearly with that 

 of the typical ascomycetes that certain stages in each group may 

 be regarded as homologous with one another, though it must be 

 allowed that the proof of the homologies is not quite perfect," The 

 description of the formation of the aecidium cup is given somewhat 

 as follows: The earliest stages consist of a tangled weft of hyphae. 

 These enlarge, forming a dense mass which has the appearance of 

 pseudo-parenchyma. This mass corresponds very well to the peri- 

 thecium of certain ascomycetes. The hymenial cells appear at the 

 base of this mass. From these club-shaped "basidia" the spores are 

 abstricted to form rows. In his theoretical discussion DeBary sug- 



I 



gests the possibility of the hymenial layer having its origin in some 

 lar^e central female organ at the base of the aecidium. He was 



^w v,..^x..«.x *v,xx.^^v. v^Xq 



unable, however, to harmonize this view with what was known of the 

 caeoma type of the aecidium. 



In 1888, Massee (18) figured and described a peculiar organ 

 occurring in the aecidium of Uromyces poae Rab. He made sections 

 of the infected leaves of Ranuncuhis ficaria, and these sections were 

 kept alive and studied as the processes went on. Massee found a 

 large club-shaped branch at the base of the future pustule. A smaller 

 antheridial cell was formed near by and fused with this oogonium, 

 but the union was not clearly made out. The antheridium became 



