RUST FUNGI— UREDINEAE 243 



the most part aculeolate or minutely punctulate. The teleuto- 

 sporiferous sori are also variously coloured, and very rarely 

 furnished with a pseudoperidium. The teleutospores are either 

 continuous or septate, generally sup- 

 ported on a persistent peduncle, 

 externally smooth, or ornamented in 

 various ways by spines, warts, gran- 

 ules, or other appendages, germinat- 

 ing through determinate pores. By Fis. 115.— "Cluster-cups "of 

 germination of the teleutospores a Aetidia. 



promycelium is developed, which is typically four -septate, 

 bearing sporidiola at the apices of sterigmata. This, therefore, 

 is the normal sequence of fructification — spermogonia, aecidia, 

 uredospores, teleutospores, and sporidiola — but some one or more 

 of the series is often suppressed. 



The arrangement adopted most generally is, to a great 

 extent, an imperfect one, since it assumes a knowledge of the 

 most important features in the life -history of each species. 

 This may be all very well for a local flora, where details may 

 be determined, but it is of doubtful value in dealing with a 

 mass of exotic species, where special information is not to be 

 obtained. It is an open question whether all sound classification 

 should not be based upon characters which may be determined 

 directly from the individuals themselves, and should include 

 nothing which is not present or evident in examples of any 

 given species. The entomologist finds no difficulty in classify- 

 ing his Lepidoptera, although they may have passed through 

 previous stages wholly different from that presented by the 

 imago, and his classification is based upon features to be found 

 in the perfect insect, and in those alone. Is it so with the 

 species of Puccinia, for example ? if recent disclosures are to 

 accepted. There is a certain species called Puccinia phragmitis, 

 which is found growing upon Phragmitis communis; and there 

 is a second supposed species called Puccinia Trailii, which 

 occurs upon the same host ; and there is still a third species 

 which has been named Puccinia Magnusiana, having the same 

 habitat. How are these species proposed to be distinguished, 

 except by the intuitive knowledge that the Aecidium of 

 Puccinia phragmitis is supposed to flourish on the leaves of 



