244 BOTANICAL GAZETTE [MARCH 
Isthmospora, gen. nov.—Mycelium and conidiophores dark. 
Conidia consisting of two approximately equal halves connected 
by a narrow isthmus, dark. The type of the genus is J. spinosa. 
The species here characterized are of very unique form. They clearly 
belong to the Fungi Imperfecti, Dematiaceae, and in this family can only find 
kinship in that heterogeneous group the Staurosporae, among which, however, 
there is no genus closely related to the present forms. They differ from 
Desmidiospora, which has two conidial forms and a hyaline mycelium, in the 
absence of both of these characters. There is some resemblance to Spegazzinia 
and Tetracoccosporium, which have been placed in the Tuberculariaceae. The 
difference in spore structure, however, is sufficient to separate the genus 
Isthmospora from both of these. 
Isthmospora spinosa, sp. nov. (fig. 17).—Mycelium fine, 1-2 », 
pale brown, aggregated into dense knots enveloping parts of the 
host mycelium. Conidiophores short, but slightly differentiated 
from the mycelium. The spores viewed from above are seen to 
consist of 4 major cells which are dark colored and rather thickly 
set with spines, each spine about 1 » long. The major cells are 
arranged in two pairs which are connected by a 2-celled isthmus. 
This isthmus is flanked on either side by a circular, hyaline cell. 
Dimensions: total length 17-24, breadth 14-20, isthmus 
3~4 mu wide, hyaline cell 3—4 uw in diameter. 
On Meliola psidii Fr. on Psidium guajava, 3120 (type), Yauco, 56424, 
Jajome Alto. On Meliola chiococcae Stev. on Chiococca alba, 7743, Vega Baja. 
On Meliola byrsonimae Stev. on Byrsonima lucida, 3541, Guayanilla. On 
Meliola smilacis Stev. on Smilax coriaceae, 5261, Manati. On Meliola helleri 
E. on Myrcia splendens, 5646, Jajome Alto. On Meliola praetervisa Gaill. on 
Coccolobis sintenisii, 7066, Mayaguez, and on Coccolobis pyrifolia, 7065, Maya- 
guez. On Meliola philodendri Stev. on Philodendron krebsii, 7225, Arecibo- 
Lares Road, 8994, Maricao, 4346, Ponce, 8712, El Alto de la Bandera. 
Isthmospora glabra, sp. noy. (fig. 18).—Mycelium fine, 1-2 #, 
pale, aggregated into knots on the host mycelium. Conidiophores 
short, slightly different from the mycelium. Spores of 4 major 
cells in 2 pairs connected by an isthmus; isthmus dark, major cells 
pale straw to wine colored, glabrous; total dimensions 9 X 10 H- 
On Meliola melastomacearum Speg. on Clidemia hirta, 9479, near Utuado. 
On Meliola psychotriae E. on Gonzalagunia spicata, 7793, Rio Arecibo, Rat 
7046, Mayaguez. On Meliola bicornis Wint. on Meibomia supina, 8975, Mari- 
On Meliola glabroides Stev. on Nectandra patens, 8973, Maricao, and on 
