CHAPTER XXXII. 



TARE OR VETCH, AND PEA MOULD. 



Peronospora vicice, Berk. 



LIKE several other species of Peronospora described in 

 this work, P. vicice was first detected by the Rev. M. J. 

 Berkeley, and described and illustrated by him in vol. i. 

 of the Journal of the Royal Horticultural Society in 1846. 



This parasite is frequent on the tinder surface of the 

 leaves of tares or vetches and field and garden peas. 

 Although allied to Peronospora trifoliorum, D.By., as illus- 

 trated at Fig. 1, and P. exigua, W.Sm., Fig. 2, it is 

 clearly distinct from both. Like the two plants just 

 described, it grows within the foliage and causes brownish 

 downy patches on the leaves and putrescence of the 

 tissues. The conidiophores of the fungus grow in 

 clusters, the spores are supported on long extremely 

 slender spicules, and are tinted with a dull gray 

 colour. Peronospora vicice, Berk., is illustrated, enlarged 

 400 diameters, at Fig. 122; a single spore or conidium 

 is farther enlarged to 1000 diameters at A. The spores 

 on germination do not burst at the apex, but the germ- 

 tube is generally protruded from the side. Damp close 

 weather greatly favours the extension of this fungus, and 

 dry weather retards its growth. It unfortunately happens 

 that late peas are sometimes quite destroyed by another 

 fungus named Erysiplie Martii, Lk., whose growth is 

 favoured by dry weather and retarded by wet. When 

 both fungi are present on one crop the destruction of 

 peas is complete. 



The resting- spores are brown, and at length reticulated 



