SPH^ROTHECA, Lev. 



Ann. Sci. Nat. Series III, Tome XV, p. 138. 



Perithecia containing only one ascus. Appendages simple threads 

 not unlike the mycelium with which they are frequently interwoven. 

 Ascus suborbicular, usually containing eight sporidia. Very rarely 

 two asci have been observed. 



S. pruinosa, C. & P. Erysiphei of the U. S. in Journ. Bot. 1872. 



Hypogenous. Mycelium thin, effuse, persistent. Perithecia scat- 

 tered, 80-100 [i ; cell-reticulations small, appendages few, simple, rigid, 

 even, hyaline, 3-4 times the diameter of the perithecium. Ascus ovate. 

 Sporidia 8, 20-25 ju long. ' 



On Rhus typhina, R. glabra and R. copallina. From New 

 York to Missouri, and no doubt more widely distributed ; not very 

 common. (The perithecia appear to develop earlier and better on the 

 galls of a Phytoptus affecting these host-plants). 



S. Hiimuli, (DC.) 



Erysiphe Humuli, DC. Flore Franc. VI, p. 106. 



Sphczrotheca Castagnei, I,ev. in part, Ann. Sci. Nat. XV, p. 139. 



SphcErotheca Hamuli, Burrill, Parasitic Fungi of Illinois, II, p. 400. 



Mostly hypophyllous. Mycelium inconspicuous or evanescent. 

 Perithecia scattered, abundant, mostly rather small, 75-95 /i, wall- 

 texture firm and compact, though thin, surface smooth, reticulations 

 small, often obscure, usually less than 15 p.) appendages slender, three 

 or more times as long as the diameter of the perithecium, usually col- 

 ored throughout when mature, mostly free from the mycelium. Ascus 

 broadly elliptical or suborbicular. Sporidia usually 8, large, averag- 

 ing 20 p. long. 



On Viola canina var. sylvestris, Geranium maculatum. G. 

 Richardsoni, G. incisum, Spiraea, Physocarpus opulifolia, Rubus 

 odoratus, R. triflorus, R. strigosus, R. hispidus, Geum album, G. 

 Virginianum, G. macrophyllum,, Fragaria, Potentilla palustris, 

 P. anserina, Poterium, Agrimonia Eupatoria, Gilia gracilis, G. 

 linearis, Humulus lupulus. 



This species probably occurs on many other hosts, especially upon 

 other Rosacea?, upon which the fungus has usually been identified as 

 S. Castagnei. 



Common throughout North America east of the Rocky Mountains. 

 In California Dr. Harkness reports S. Castagnei on hop leaves. This 

 is no doubt what is here called S. Humuli. 



It is exceedingly difficult to determine from literature upon what 

 hosts S. Humuli occurs, because it is very rarely separated from 



