134 DISEASES OF FIELD & GARDEN CROPS. [CH.XX. 



similar with the one which, preceded their own Erysiphe 

 condition. 



Dr. H. W. Harkness has described, hefore the Micro- 

 scopical Society of San Francisco, pycnidia upon the 

 spawn of this fungus as found in California. Pycnidia 

 are small conceptacles containing stylospores, or spores 

 after the nature of conidia. The "white rust," as it has 

 been termed in America, first appeared in California in 

 1877 on mature wheat. In that year it covered half a 

 million acres of wheat, destroying some of the crops. 

 We have taken pains to completely illustrate this com- 

 mon, curious, and destructive fungus, for, as far as we 

 know, no complete illustrations have hitherto been given. 

 LeVeille's illustration, generally referred to, in the Ann. 

 des. Sc. Nat., vol. xv., 1851, t. 10, f. 33, is very bad. 

 It shows the appendages branched and the asci without 

 sporidia ; the scale of magnification is also omitted. 



Hops, peas, beans, roses, and many other plants, are 

 preyed upon by fungi very closely allied to the fungus of 

 grass blight. 



Grass blight is synonymous with bad, impoverished 

 grass, with mildewed hay, and ill-nourished herds and 

 flocks. The life of the fungus which causes the blight 

 is preserved through the winter in decaying mildewed 

 grass and straw. These facts therefore teach us that all 

 mildewed material should, as far as possible, be gathered 

 together in the late autumn or winter and destroyed. If 

 all the autumn-borne perithecia are destroyed it is obvious 

 there can be no Oidium in the spring. The destruction 

 of all infected material is perhaps impossible, but all the 

 facts known in reference to the fungus of this disease 

 point to the great desirability of clean farming, and to 

 the necessity of destroying as much mildewed grass and 

 straw refuse as possible. If all farmers would agree to 

 one course of action the bad effects of diseases like the 

 one here described would be greatly lessened. 



