58 A Monograph of the Erysipfiaceae 



A species of SpJiaerotJicca was published as S, pruinosa by 

 Cooke and Peck, in 1872, with the following diagnosis : ** Am- 

 phigenous. Mycelium effused, arachnoid, subpersistent. Con- 

 ceptacles minute, globose, scattered. Appendages {^w^ inter- 

 woven, colorless. — On both surfaces of leaves of Rhus z^abra, 

 Albany, New York. Habit and character of mycelium very dis- 

 tinct from 5. pannosa. The colorless appendages will not permit 

 of its being confounded with 5*. Castagnci. Sporidia .0007— .0008 

 in. X .0004 in.'' Examination of the type specimens on Rhus glabra, 

 and of others on R, copallma, shows the fungus to possess these 

 characters : mycelium persistent, thin, and effused, perithecia 

 more or less scattered, 70-105 a in diameter, cells small, 8-1 s u 

 wide ; appendages rather few, variable in length, sometimes, 6 times 

 the diameter of the perithecium, usually shorter, more or less 

 flexuous or angularly curved, usually more or less refractive and 

 shining white throughout, with the lumen obliterated, sometimes 

 brownish at base, very rarely pale brown nearly to the apex ; ascus 

 elliptic-oblong to subglobose, 70-90 /ix 50-65 ft, spores 8, 22-25 



XI2-I5,«. 



As Cooke remarks, the habit and mycelial characters separate 

 the plant from S. pannosa, and the affinity is certainly wholly with 

 5. humuli, to which species, indeed, I have felt obliged, for the 

 reasons given below, to unite this form on Rhus. When investi- 

 gating the so-called '* S. pannosa" of many American mycologists 

 I was at once struck by the resemblance of some specimens of 

 this fungus on Rose-leaves to " S. pruinosa:' In the first speci- 

 men examined, "on cult, roses, Madison, Wis., i88q (Henry)" 

 (in the Herbarium of the Missouri Botanic Garden), the re- 

 semblance was so close that there could be no doubt that 

 the fungus on Rhtis and this on Rosa belonged to the same spe- 

 cies. At that time I thought it might be possible, relying on the 

 white shining appendages to keep the plant distinct from 5. humuli. 

 Since then, however, I have seen more material of this fun^rus on 

 American roses. For this I am indebted chiefly to Professor 

 Seymour and Professor Clinton, and the specimens sent (now in the 

 Kevv Herbarium) show clearly that although this fungus on Rosa 

 has in many examples, quite coloriess appendages like those of 

 " i*. pndnosa," in others it may show distinctly colored appendages. 



