154 MICEOSCOPIC FUNGI. 



Turnip Mould. — Since tlie advent of tlie potato 

 murrain a similar disease has been witnessed, 

 thougli more limited in its extent_, amongst 

 Swedish, turnips, commencing in little waved 

 irregular hues following the course of the vessels, 

 around which spots are formed by the deposition 

 of dark granules in the same manner as in the 

 potato. In this instance, the leaves apparently are 

 first attacked in a similar manner by a species of 

 mould or Peronospora alKed to the one already 

 described, but which has been long known as 

 parasitic upon cruciferous plants, to which the 

 turnip belongs. This species, termed Peronospora 

 parasitica, is white in all stages of its growth. It 

 is much more branched, and the branches are com- 

 paratively shorter than in the potato mould, and 

 the tips of the branches are bifid (fig. 262). The 

 acrospores are very large and globose, features 

 also which distinguish this mould from the last. A 

 short time since we were called to witness a bed of 

 splendid cauliflowers, which had, up to that time, 

 been the pride of their cultivator ; but, alas ! their 

 glory was threatened with speedy annihilation, for 

 in nearly every instance the lower leaves had 

 become more or less covered on their upper surface 

 with yellow spots, and beneath glaucous with the 

 mould we have been describing. The diseased 

 leaves were all immediately removed, but we fear 

 without success, although no positive information 

 has since reached us. The almost unnatural 



