162 MICROSCOPIC FUNGI. 



was to be seen by the aid of a lens, scattered over 

 the nnder surface of the leaves. By the micro- 

 scope, the branched threads, having the tips 

 furnished with sub-elliptic spores, were revealed, 

 and an ally of the potato mould found revelling 

 amongst the roses. 



During the winter of 1863-4, we found the leaves 

 of several species of dock occupied by a mould 

 which appears to be a very low form of Peronospora. 

 Its presence was indicated by brownish orbicular 

 spots, on which the fertile threads occurred in 

 small bundles. These threads were generally 

 simple, but occasionally forked, bearing rather large 

 elliptical acrospores attached obliquely to the tips 

 of the threads (fig. 269). In consequence of this 

 peculiarity, we have named the species, which does 

 not appear to have been noticed before, Peronospora 

 obliqua. It is clearly very distinct from another 

 species found on dock leaves by Corda. 



Of the remaining British species, one (P. 

 Arenarice) is found on the leaves of the three- 

 veined sandwort (fig. 268) ; another attacks the 

 red corn-poppy, a third is found on the common 

 nettle, one on the brooklime, another on the 

 wood-anemone (fig. 267), and another on the fig- 

 wort. 



Doubtless all the species in this genus are 

 possessed of the third means of reproduction, by 

 zoospores, as discovered in the potato mould, not 

 only from the acrospores, but also from the oospores. 



