248 P. J. BUTLER. 



In coconuts the fruit is affected. None of those formed after 

 the symptoms of the disease are visible externally, develop properly ; 

 they drop one by one while immature. Those formed somewhat 

 earlier may ripen, but are often of inferior quality. 



VII. — Description of the Parasite. 



Pythium palmivorum belongs to a genus of the most primitive 

 group of the fungi, the Phycomycetes or alga-like fungi. The char- 

 acters of this genus have been sufficiently described in a previous 

 number' of this series, and need not be considered in detail here. It 

 is composed partly of aquatic and partly of terrestrial forms, several 

 of which are parasitic on other plants. The terrestrial forms are 

 nearly all soil-dwellers, two only, the present species and P. Indigo- 

 ferse But!., inhabiting the aerial parts of plants. The description 

 of P. palmivorum, previously published, requires to be amplified as 

 a result of further examination. 



The body of the fungus consists of branching threads or "hyphse" 

 forming in the aggregate a web or " mycelium/' which may be 

 entirely buried in the palm tissues or may be partly superficial on 

 the surface of the leaf-sheaths, where it frequently develops so as 

 to form a thick white felt over the disease-spots. 



The hyphse, which are very irregular, measure on an average 

 5/u ( J /'^^^^ miUimetre) within the tissues but are often larger, especially 

 in the superficial felted mass where they may be up to 8/« They 

 are continuous hollow threads, not being divided by cross-walls, 

 except in rare cases, particularly near where the organs of propaga- 

 tion are formed. Within the tissues they occur in the intercellular 

 spaces, and also force their way between adjacent cells, becoming 

 irregularly compressed and contorted in so doing. They are 

 nourished exclusively from the living cells of the host-plant, 

 into which they send fine prolongations known as " haustoria " 

 or suckers. 



1 Butler, E. J. An account of the genus Pythium and some Chytiidiacese. Memoirs 

 of the Dept. of Agric. in India, Vol. I, No. 5, 1907. 



