PERONOSPORA 113 



with a distinct apiculus or projecting wart at the apex, but 

 typical of the genus in all other respects. 



Plenty of air and sunshine and not too much water will 

 arrest the disease. 



Peronospora lamii (De Bary) is met with on labiate plants, 

 as the dead nettles, Stachys, Salvia, etc., where it forms 

 broadly effused, dingy lilac patches of mildew on the under 

 surface of the leaves 



Conidiophores short, several times branched, ultimate 

 branches generally long and pointed, 17-25x15-20. 

 Oospores globose, brown, 30 /i diam., wall slightly wrinkled. 



C. Wall of oospore warted. 



Peronospora arenariae (Tul.) is met with on caryophylla- 

 ceous plants, as chickweeds, stitchworts, etc. 



Conidiophores slender, repeatedly branched, ultimate 

 branchlets very slender, straight, conidia elliptical, 20-25 x 

 14-16 {jl. Oospores globose, brown, wall with rather large 

 warts, 24X30/* diam. 



D. Wall of oospore netted. 



Peronospora viciae (De Bary) grows on the leaves of 

 leguminous plants, as broad beans, various wild vetches, 

 Orobus, Melilotus, etc. The mildew often forms a dense 

 greyish felt on the under surface of the leaves. 



Conidiophores repeatedly branched, ultimate branchlets 

 pointed, short, conidia elliptical, 25-28x15-18 fi. Oo- 

 spores globose, pale brown, wall with a wide meshed 

 network. 



Peronospora myosotidis (De Bary) occurs on boraginaceous 

 plants, Myosotis, Symphytum, Lithospermum, etc. 



Conidiophores slender, elongated, much branched, termi- 

 nal branchlets very slender, conidia elliptical, 20-24X14-18 

 \i.. Oospores globose, brown, wall with a large meshed 

 network, 25-30 /x diam. 



Peronospora calotheca (De Bary) occurs on plants belonging 

 to Galiaceae, as species of Galium, Asperula, Sherardia, etc. 



Conidiophores many times branched, ultimate branchlets, 

 very slender, conidia elliptical, 25-30X14-17 /'. Oospore 

 globose, brown, wall with a fine meshed network. 



H 



