PAPERS ON BOTANY 265 
XI.—CERCOSPORA CARBONACEA SP. nov. 
Spots amphigenous, very conspicuous on upper side of leaf, 
burned or charred in appearance, usually angular, limited by 
veins or veinlets, somewhat elevated, becoming one or one and 
one-half centimeters in diameter; on the lower side of leaf, 
brown, becoming darker with age. Conidiophores fasciculate, 
10-20 in a cluster, arising from a stoma, erect, 1-2-septate, 
dark, simple, unbranched, smooth or somewhat geniculate to- 
ward the apex, 50-80x4-5 microns. Conidia single, cylindrical 
always curved near one end, cane-shaped, 4-8-septate, slightly 
narrower at the straight end, very dilutely colored, 70-100x6 
microns. (Fig. III.) 
/; 
Fig. 3 
On living leaves of Dioscorea alata, L. in Porto Rico: Vega 
Alta, 4178; (type); Vega Baja, 4234; Cabo Rojo, 6469; 
Afiasco, 3563; St. Ana. 6687. 
EXPLANATION OF FIGURES 
Fig. I—Helminthosporium leaf-spot on Paspalum conju- 
gatum. 
Fig. Il—Helminthosporium mayaguezense; (a) conidio- 
phore; (b) spore. 
Fig. I1]—Spores of Cercospora carbonacea. 
