io6 DISEASES OF CULTIVATED PLANTS 



inner layers, white at first, then brown. These commence on 

 the outer sheaths first, and gradually work inwards. The 

 patches are dry at first, and sometimes covered with a felt of 

 white mycelium. At a later stage a wet rot follows, other 

 organisms join in the act of destruction, and the primary 

 cause is lost sight of. 



Forming large patches of felty white mycelium on the inner 

 surfaces of the leaf-sheaths. Sporangia inverted pear-shaped, 

 less frequently globose, formed in the weft, and not raised on 

 special sporangiophores, averaging 50X35 /*; zoospores 

 after coming to rest, 8-10 /*. Oospores globose 35-45 /*, 

 formed in the weft of mycelium, always extra-matrical. 



When a tree is once attacked, recovery is hopeless, hence 

 the head of every infected tree should be cut off and burned 

 at the earliest stage of disease ; by such means infection of 

 other trees would be prevented. This method should be 

 general to be of any real service. Healthy trees in the neigh- 

 bourhood of infected ones should have leaf-sheaths brushed 

 with Bordeaux mixture just before the removal of diseased 

 trees commences. 



A somewhat similar bud-rot of cocoanut palms is also pre- 

 valent in Cuba and the West Indies, also in Ceylon. By 

 some this is considered as a bacterial disease, by others as 

 due to a fungus. The cause will probably be proved, when 

 thoroughly investigated, to be the same as the Indian one. 

 All are agreed that the preventive method given above is the 

 most certain if thoroughly carried out. 



Butler, Agric. Journ. of 'India , i, p. 304 (1906). 



Pythium intermedium (De Bary). This fungus has been 

 recorded as proving very injurious to the prothalli of ferns, 

 especially when raised from spores and grown under glass. 

 The fungus enters the tissue of the prothallus, which soon 

 wilts, becomes dark in colour and dies. Rare in this country. 



Conidia globose, terminal in chains of 2-5, the terminal 

 one largest. Sexual reproduction unknown. 



1 If the pots or vessels in which the prothallia are grown 

 are rested on sphagnum, a layer of which can be placed in 

 the bottom of the Wardian case, and after the young prothallia 

 have started, all of the watering be applied through this, the 

 prothallia will do much better than if surface watering is 

 practised, and far better than where the pots are rested in a 



