AT FAYRTTE, low v 



Erysiphese. 



These fungi are parasitic on various angiosperms and are among 

 the most noticeable of parasitic fungi. Yet, to one who has not given 

 the matter attention, the number of species and hosts in one locality is 

 surprisingly large. Some species are so inconspicuous that they would 

 not be noticed by an inexperienced collector, and in other cases they 

 seem like a pubescence on the leaf. 



The vegetative portion {mycelium) appears like a white web closely 

 fixed to the host, by means of haustoria, above, below, or on both sides 

 of the leaf, though sometimes found on other portions of the host. 

 When this mycelium is conspicuous, the fungus is easily found, but in 

 some instances it is inconspicuous. 



The reproductive organs are of two kinds, sexual and asexual. The 

 The asexual organs are called conidia and are arranged one above 

 another on erect branches {hyphic) of the mycelium. They separate at 

 maturity, blow about and germinate, thus providing for the immediate 

 and rapid increase of the species. The sexual organs are ot two kinds, 

 antheridia and carpiogonia. They are also borne on the mycelium at 

 points where two branches cross. The antheridium corresponds to the 

 stamen of a flowering plant, and the carpogonium is analogous to the 

 pistil. After the carpogonium has been fertilized by the antheridium, 

 it developes into the perithelium, which corresponds to the fruit of a 

 flowering plant. The perithecia contain vessels called asci, and these 

 asci enclose the sporidia, which germinate and produce the plant the 

 following year. These perithecia with their contents furnish the 

 principal means of classifying the Erysipheae. They appear as little 

 specks, varying from brown to black in color. Sometimes they are so 

 small as to be scarcely visible to the unaided eye, but usually thev will 

 be seen on careful examination. A good pocket lens will enable one to 

 distinguish them from dirt or other fungi. 



The asexual and sexual organs are sometimes found at the same 

 time, but not always. The former are generally produced earlier than 

 the latter, which are not usually found till in the fall, or sometimes not 

 till after the leaves have fallen. The perithecia fall from the leaves or 

 with them and germinate the following spring. The conidia are not 

 supposed to endure the winter, though in some cases where the 

 perithecia are seldom found, it seems possible if not probable that they 

 do. 



The blights are often very injurious to useful and ornamental culti- 

 vated plants, even infesting those kept in the house. I watched a 

 chrysanthemum, belonging to Dr. C. C. Parker, till the leaves were 



