JEHANGIR FARDUNJI DASTUR. 179 



rain we had in April and May. The disease disappears by the begin- 

 ning of September, at the end of the rains. About nineteen varieties 

 were grown on the Pnsa Farm in 1911, but none of them escaped the 

 attack of this fungus, not even the indigenous Patna variety. 



In no paper dealing with castor cultivation except in one has 

 any reference been made concerning the high mortality of the 

 seedlings or concerning the characteristic brown leaf spots found 

 on leaves of young and old plants. 



Darrah 1 reports that in the year 1889 " a very large number 

 of young castor plants, even those from the indigenous Cachar 

 seed, had damped off " on account of damp and excessive rain. 

 Mr. Mackenzie, who was in charge of the m'-silk experiments, 

 observed that the seedlings damped off and died " before they 

 matured a sufficiently hard skin or bark on their stems." 



This damping off of seedlings in water-logged places is what I 

 have found on the Pusa Farm to be due to Phytophthora parasitica. 

 In all probability therefore Phytophthora was the cause of the large 

 destruction of castor seedlings of Mr. Mackenzie's crop in 1889. 



This parasite is the most injurious of the fungal parasites of 

 castor ; it destroys seedlings and attacks leaves of older plants. 

 My thanks are due to Mr. M. N. De, the Sericulture Assistant at 

 Pusa, for carrying out experiments to see the effect of feeding en-silk 

 worms on leaves attacked by Phytophthora. He informs me that 

 the worms refused to eat the diseased portions of the leaves, and 

 that their growth when fed on diseased leaves was very slow as 

 compared with those fed on healthy leaves. 



In the case of a monsoon (Kharif) crop the most critical period in 

 its life history is when the seedlings are about six to eight inches 

 high and when their stems are quite tender. In low-lying water- 

 logged and badly drained fields about thirty to forty per cent, 

 of the seedlings damp off. The first indication of the disease is 

 the appearance of a roundish patch of an unhealthy dull green 

 colour on both the surfaces of a cotyledon. It soon helplessly 



* Darrah, H. Z. The JJrt-silk of Assam, 1890, p. 15. 



