L. S. SUBRAMANIAM 191 



Morphology of the Fungus. 



The mycelium is composed of much branched hyphae, sometimes showing 

 false dichotomy, very variable in breadth from 3 to Sfi. ' Septation occurs very 

 irregularly in old cultures. Irregular swellings on the hyphse were quite 

 common, when grown on plant tissues or in water culture. In glucose agar 

 the hyphse are not very broad, and in old cultures they are often septate. In 

 maize and wheat meal the growth of the mycelium is luxuriant and the hyphse 

 uniform in breadth. In French bean agar the growth of the mycelium is not 

 very luxuriant. On boiled ants the mycelium is very rich in protoplasm and 

 the hyphse broad. The formation of the sporangia is the same as described 

 in Pythium gracile} The sporangial stalk is not cut ofE by a septum from 

 the parent hypha, but in badly nourished cultures a septum may occur at the 

 base (PI. V, fig. 6). The irregular swellings on the hyphse serve as reservoirs 

 of protoplasm, and under favourable conditions sporangia may develop from 

 them. It is not uncommon to find empty cells at the base of the sporangial 

 hyphse. Sporangia have not been observed on solid media. The develop- 

 ment of sporangia and oogonia follows no regular sequence. WTien cultures 

 are kept in a cool incubator at 21 °C., oospores appear first and later on 

 sporangia. At'30°C. sporangia appear first. ' , 



The zoospores are from a few to 35 or more in number in each sporangium. 

 They are bi-ciliate, bean-shaped, slightly depressed at the hilum where the 

 two long cilia are attached, and measure when moving 8 to llfi, 6 to 8/a in 

 diameter, and when they come to rest 7 to llji. They germinate by one or 

 more tubes, which on growing sometimes become septate. No special effect 

 was seen on the discharge of zoospores as a result of lowering the temperature 

 except the delayed formation of sporangia. 



The oogonia are formed generally on short lateral stalks but sometimes 

 are intercalar. They are also formed on the bud-like growths developed in the 

 normal mycelium. They are spherical or sometimes slightly longer than 

 broad, thin-walled, hyaline, and measure 18" 7 to 33/u in diameter. 



The antheridia may be terminal, or intercalar, or hypogynal. There is 

 generally one antheridium for each oogonium but in rare cases two may be 

 present. The antheridium generally rises from a different branch from that 

 which carries the oogonium but in rare cases from the same branch. At times 

 two antheridia are formed side by side on the same hypha intercalarly, and 

 fertilize different oogonia.' The, terminal antheridia are club-shaped with a 



1 Butler.' Loc. cit., p. 68, PL I, fig. G. 



