82 BOTANICAL GAZETTE [ AUGUST 
ther distinguished from G. naviculisporum by the development of 
a stroma in old cultures on sterilized bean stems. 
Gleosporium cactorum, n. sp. (jig. 74); on Cactus sp. 
There is a member of the genus Glceosporium which infests 
the cactus in greenhouse cultivation. The acervuli are erum- 
pent-superficial, pale pink, becoming dark colored, situated on 
dark brown, decayed spots. On the margin of the spots the 
acervuli become confluent, often forming a close ring surround- 
ing the less gregarious acervuli of the central portion. The 
conidia are elliptical, with rounded ends, and measure 12-17 
x 4-6. 
The conidia germinate readily in nutrient agar, and growth 
takes place rapidly. The colony has a white, snowflake 
appearance, belonging to a group showing a loose, open growth 
at the center, with the slender radiating strands of mycelium 
growing from the central point. The growth of the mycelium 
above the surface of the agar gives the colony a downy oF floc- 
culent appearance.. The marginal mycelium presents a less 
regular growth than is seen in the open centered colony of 
Colletotrichum gleosporoides, and the open center is usually less 
distinct. By comparing the colonies with those of G. cingulatum 
Atk. (see fig. 26) a close resemblance will be observed. - The 
latter, however, differs in the looser, irregular marginal growth, 
as well as in morphological characters, which will be discussed 
more at length in connection with that species. 
On bean stems a dense growth of white mycelium is Pf 
duced, which shows later a slight development of strqae 
appearing along the edges of the stems. A well developed 
stroma is formed at the base of the acervulum. The conidia 
ooze out in light pink masses. Associated with the acervuli are 
compact stromata, forming dark spherical elevations of the 
aeons Their appearance suggests perithecia, but no indication | 
of asci has been found in connection with the species. fig. Ty 
‘Tepresents colonies of the same species collected from 4 differ- 
ent variety of cactus a year later. 
