Stone: A new species of Puccinia 551 



This rust has a close resemblance to P, afigustata Peck on 

 Scirpus atrovirens. The teh'ospores are of about the same size and 

 shape and have the same position on the leaf. However the sori are 

 rnore scattered, a little h'ghter in color and do not become conflu- 

 ent. The most prominent difference between the telia becomes 

 apparent upon examining a section through a sorus. In all the 

 specimens of /I angiistata which I have been able to secure, there 

 is a very prominent development of the hyphae in the large inter- 

 cellular spaces of the leaf, especially immediately under a sorus. 

 In fact the very large intercellular space between the vascular 

 bundles is almost filled with hyphae. In P, aiigiistatoides this 

 development is much less pronounced, although the space between 

 the vascular bundles is filled with stellate cells and would, apparently, 

 offer a much better chance for the hyphae to develop. In study- 



FiGURE 4, Section through a sorus of P. angudatoides on Rynchospora corntcu- 

 laia^ X ^^- This sorus Is more superficial in every way than that of -P. angustata, 



ing the fungus this was the first thing to become apparent. Also, 

 the telia are much more deeply sunken in P. angustata Peck. 



4- 



The most distinctive difference between these two rusts is 

 found in the uredinia and uredinlospores. The uredinia in P. 

 angitstatoides are a little darker than in P. angustata, are more 

 definite, scattered, rarely confluent. The urediniospores of P, 

 angiistatoides are several p. smaller than those of P, angustata, 

 19-22 /i X 10-17// as against 21-30/i x 1 6-21 /i ; they are sub- 

 globose to obovoid as against globose to elliptical in P, angustata. 

 The last point of difference lies in the distribution of the germ- 

 pores. In P. angustata the pores are 2, opposite and approxi- 

 mately equatorial ; in P. angusiatoldes they are considerably above 

 the equator, at least half way to the distal end of the spore, two 

 in number and without a prominent thickening of the wall. 



