XIV.] 



SURFACE MILDEW OF TURNIPS. 



77 



the Peronospora, next described in this work. When a 

 minute slice, as just mentioned, is examined under the 

 microscope and enlarged 400 diameters, it will be seen as 

 illustrated at Fig. 27. The fungus grows on both sur- 

 faces of the leaf, and springs in both positions from a 



X-400 



FIG. 27. SURFACE MILDEW OF TURNIPS. 

 Oidiim Balsamii, Mont. Enlarged 400 diameters. 



dense stratum of matted and jointed spawn, as shown at 

 AA. From these horizontal spawn - threads arise in- 

 numerable vertical club-shaped growths, each club being 

 furnished with three joints and surmounted by a barrel- 

 shaped spore or conidium, as shown at BB. The cells at 



