RUST FUNGI— UREDINEA E 249 



spores catenulate. Here, then, we have the spermogonia, aecidia, 

 and the uredospores, which may possibly prove to form parts of 

 unknown cycles, the position, affinity, and association of which 

 must be left to the chances of future investigation. 



During late years there has been no lack of investigation 

 and observation on the structure, growth, and development of 

 the Uredines, which have mostly taken the form of artificial 

 cultures. Whether the same results take place, and in precisely 

 the same manner, in a state of nature, cannot be affirmed, whilst 

 some present grave reasons for doubt. It is still possible that, 

 if the facts are accepted, the inductions may be wrong. When 

 it is argued that certain experiments succeed in producing upon: 

 certain plants the identical Uredines which would have been de- 

 veloped in the ordinary course of nature, a sceptic will naturally 

 inquire for the evidence which proves that the resulting Uredines 

 were really produced by inoculation, or whether the elements 

 were not already present, and that these were simply stimulated 

 by the introduction, or intervention, of other agencies, and hence 

 not actually produced by inoculation. Common sense would 

 allow that, if the resulting Uredine were foreign to the par- 

 ticular species of plant, the assumption of inoculation would be 

 more convincing. This is not the place to enter upon a dis- 

 cussion of the doubts and dangers which attach to inductions 

 from the results of artificial cultures, hence it must suffice to 

 suggest that such doubts and dangers may still continue to 

 exist in the minds of those who venture to hold independent 

 opinions. 



Suggestions have not been wanting of sexuality, or of 

 fertilisation which implies sexuality, in the Uredines. The 

 application of the term " spermogonia " to the small pustular 

 eruptions, which occupy the first place in the cycle, can scarcely 

 be accepted as a suggestion, but some authors have assigned to 

 the minute spore-bodies not only the name but the function of 

 spermatia. Meyen was evidently of this opinion, and he was 

 not the only one who thought that they played the part of the 

 male element. Worthington Smith has intimated that he has 

 often seen the small sporules attached to the exterior of Aecidio- 

 spores, but he was unable to trace any pollinial tube into the 

 interior. Against the supposition that they are fecundative 



