32 spermogones 



Spermogones. 



While aecidia are always subepidermal, and in the higher 

 forms sunk rather deeply in the tissues of the host, the 

 spermogones are in certain genera subcuticular and in others 

 subepidermal, bul always shallow. This doubtless corresponds 

 to the primitive form of tin- .e-idium, when the trichogynes 

 protruded through a stoma in order to catch the spermatia. 

 Wheu fertilisation was dropped, it became possible for the 

 secidia to be surrounded tor protective purposes by a continuous 

 and firm peridiura and to be more deeply sunk within the host: 

 the spermogones. being outside the range of selective evolution 

 on account of their uselessness, have retained more or less of 

 their original character. The description of those of P. Garids 

 applies essentially to nearly all, except that in certain genera 

 they are flat, not Mask-shaped, and open by a wide pore. not 

 by an ostiole, and in these and others there are no protruding 

 ti laments. 



Spermogones never appear alone; they are always accom- 

 panied or closely followed by some other spore-form, either 

 acidio-, undo-, or teleutospores. In comparatively few cas - 

 as in P. Malvacearum, have the spermogones disappeared en- 

 tirely. 



Uredospores. 



Uredospores are usually distinguished from a-cidiospores by 

 being produced singly at the apex of a short pedicel from 

 which they easily fall off: this pedicel is the homologue of the 

 intercalary cell of the aecidiospores, as was shown by Christman. 

 In certain genera, however, e.g. Goleosporium and Chrysomyxa, 

 the uredospores are produced in short chains. Uredospores can 

 reproduce uredospores for an indefinite number of generations. 

 ( )ccasionally there are two kinds, primary and secondary uredo- 

 spores: in such cases the primary ones arise from fusion-cells 

 and take the place of aecidiospores. So far as is known true 

 uredospores never arise from a uninucleate mycelium, though 

 they may spring from a mycelium which was at first uninu- 

 cleate, but became binucleate at some point in its development. 



