BUTLER AND KULKARNI. 24^ 



moist corn meal and glucose-peptone agar media) failed to 

 grow. 



The best cultures were obtained on French-bean agar, corn 

 meal and oat- juice agar'. On corn meal the growth was dense 

 and woolly and extended over the whole surface of the medium 

 fairly rapidly. On French-bean agar the mycelium spread less 

 rapidly and was not as dense as the last. On oat- juice agar there 

 was less aerial growth than the others. Prune-juice agar and 

 glucose-peptone agar gave poor thin growths. It is somewhat 

 surprising that steamed Colocasia conn should, in spite of repeated 

 inoculations, have failed to show any growth. In all the successful 

 cultures sporangia were developed, provided the temperature was 

 not too high. Oospores were much less common and were only 

 formed in French-bean agar, buried in the medium, generally 

 several near together at about one-eighth of an inch below the 

 surface. 



The sexual stage of several Phytophthoras is rarely developed. 

 In the well-known case of potato blight, Ph. infestans, it has only 

 recently been discovered (in the United States), in spite of con- 

 tinual searches during the past thirty years. It has never been 

 encountered under natural conditions (the bodies described by 

 Worthington Smith many years ago have not been accepted by 

 mycologists generally as belonging to this fungus) but has been 

 produced in artificial cultures only 2 . The same is the case with 

 the present fungus, as neither in Java, nor in Formosa, nor in India 

 have oospores been found in or on the diseased plants. It is prob- 

 able that in these two cases the absence of a resting-spore condi- 

 tion is to be correlated with the presence of a mycelium in the 

 tubers, capable of passing over from one season to an- 

 other. 



The characters of the fungus in culture may now be described, 

 little difference, except in the vigour of growth and the presence or 



1 c/. Clinton, <!. P. Artificial cultures <>f Phytophthora. Conn. Expcr. Sta. Report, 

 11)07-08, p. <S!>s, and Oospores of Potato blight, ib., Report 1009-10, j>. 760. 



1 Clinton. G. P. Oospores of Potato blight. Conn. Expcr. Sta. Report, 1909-10, p. loj. 



