400 Dastur . — Choanephora cucurbitarum , ( B . and Rav.) 
begins to rot. The rot then rapidly extends downwards, attacking buds 
and tender leaves. The affected tender parts of the stem hang limply. As 
the disease travels downwards the whole plant, in a severe case of attack, 
may be killed. The infected part of the stem shows a very marked wet 
green colour, and the bark easily peels off in shreds. 
Characters of the Fungus. 
Conidial stage. The conidiophores are erect and project at right 
angles to the epidermis. They are up to 5 mm. in length. They are 
whitish at first, but have a silvery metallic lustre when they are mature. 
They end in a capitate vesicle from which a few more ramuli arise, which 
in turn become vesicular (Fig. 1). These secondary conidiophores remain 
unbranched. From the capitella arise dense, black clusters of conidia, each 
seated on a short sterigma. Conidia are elliptical to oval in shape, finely 
striated, and light brown in colour (Fig. 2). The base of each conidium is 
provided with a hyaline appendage. The conidia measure 13-2 -24 x 
8-8-13-2/ x . 
The conidia germinate readily in water. Before germinating they 
increase considerably in size and become slightly lighter in colour. As 
a rule, a single lateral germ-tube is developed. 
Sporangial stage . On the host in nature the conidial stage only is 
found, but the other stages, viz. sporangial, chlamydospore, and zygospore, 
have been developed in cultures. In fact, except the conidial stage, no 
other stage in the life-history of this genus has as yet been observed on the 
host plant under natural conditions. Cunningham 1 found that the sporangia 
of C. infundibnlifera , (Curr.) Cunn., developed only when the fungus was 
cultivated under unfavourable conditions ; Thaxter 2 failed to get the 
sporangia of C. Americana , which is the same as C. cucurbit arum, (B. and 
Rav.) Thaxter ; but Wolf 3 succeeded in inducing them to form in 
cultures. The sporangia of the chilli Choanephora have been developed not 
necessarily under unfavourable conditions of nutrition. They are formed in 
cultures always along with the conidia, though Wolf has found the sporangia 
of C. cucurbitarum apart from the conidia. Sporangia cease to develop 
when the fungus is grown for a long time in cultures. Like C. infundibuli- 
fera> the fungus also loses after a time its vigour of growth in artificial media. 
Mature sporangia are evident as pendulous, large, black, globular 
bodies, but when young they are white in colour. They have big round 
columella (Fig. 5). The sporangial wall is smooth and colourless, the black 
1 Cunningham, D. D. : On the Occurrence of Fructification in the Mucorini, illustrated by 
Choanephora. Trans. Linn. Soc., London, Ser. 2, Bot. i, 1879, p. 417. 
2 Thaxter, R. : A New English Choanephora. Rhodora, v, No. 52, 1903, p. 101. 
8 Wolf, A. : A Squash Disease caused by Choanephora cucurbitarum. Journ. Agr. Res., viii, 
No. 9, 1917, p. 323. 
