UREDOSPORES 33 



This would be the case in a true Hemipuccinia, but none of 

 these have so far been cytologically investigated. 



Uredospores are always unicellular, except in the case of 

 a few monstrosities. Primarily they must be considered a 

 device to aid in rapid propagation and hence may be called 

 stniinier-sipores: for this reason they usually germinate with 

 great readiness when mature, always forming a tube which 

 enters a stoma of the host. The number of germ-pores varies 

 from 1 to 10 (usually 2 to -i) : only one case is known in 

 Uromyces where they possess a single pore ( U. uniporulus) and 

 one in Puccinia (P. monopora). They present a wonderful 

 sameness in shape throughout the whole group, and in colour 

 vary from yellow and orange to brown. It may be taken as 

 a general rule that if the wall is colourless, the contents are 

 yellow or orange from an abundance of that yellow oily 

 substance which occurs in ascidiospores ; if the wall is distinctly 

 brown, the contents are often colourless when mature, though 

 at first they frequently contain the usual yellow oil. It is only 

 in a few instances, in the lowest genera, that uredospores are 

 quite without colour. The uredospores of Puccinia dispersa 

 and in a smaller degree of P. graminis are noticeable for a 

 curiously dull appearance which is very characteristic, because 

 they combine orange contents with a brownish membrane. 

 The outer wall of uredospores is almost always covered with 

 spines (echinulate), needles (aculeate) or warts (verruculose) ; 

 it is very rarely smooth ; these projections enable them to cling 

 more readily to the surface of the host. They are often inter- 

 mixed with paraphyses, which are usually clavate or capitate 

 in shape ; these are found in a few species of Puccinia, but 

 more especially in Melampsora and Phragmidium. These 

 paraphyses are homologous with the spores, being binucleate 

 at first, but the nuclei soon disintegrate. 



There is very frequently found in the uredo-sori of many 

 species a parasite belonging to the Deuteromycetes, called 

 Darluca Filum. It consists of a black pycnidium, enclosing 

 numerous uniseptate pycnospores which are faintly apiculate 

 at each end. This has been sometimes mistaken for another 

 spore form of the Uredine. 



G. u. 3 



