My ee ae 
321 
of their development, and are of a firm cheese-like consistency. 
Their distribution in the cortex contrasts markedly with that 
discrete entities without intermediate structures, and may be 
formed simultaneously, for examples of each in various stages 
of growth are to be found side by side. Whatever the factors 
conidiophores, they evidently bear a direct relation to the lenti- 
cels. It is improbable that this stimulus is one of aeration for 
it is difficult to conceive that this could have so local and so 
Distribution of Fungus in the Wood.—The symptoms of 
extreme drought presented by the specimen had aroused the 
explanation of this was given by radial longitudinal sections 
for in these it was seen that the mycelium was almost totally 
confined to the living tissues of the central cylinder. From the 
cortex the fungus passed into the medullary rays which it 
traversed in a radial direction, and in which it was so abundant. 
as to form the most prominent feature in stained sections, often 
completely filling the cells of this tissue with masses of fungal 
hyphae. e mycelium also invaded freely the cells of the wood- 
parenchyma, but only very rarely could a filament be discovered 
in any of the water-conducting elements of the stem or in the 
dead mechanical fibres. The fungus was absent from the pith 
although ray cells bordering on this tissue contained the fungus 
in quantity. Sections were taken from all portions of the affected 
zone, and the constancy and exactitude of this differential dis- 
tribution confirmed. 
Cause of Death of Host.—The absence of the mycelium from 
the vessels and tracheids immediately proved the original diag- 
nosis to be erroneous, for this was based on the assumption that 
the water-conducting elements of the stem were choked by masses 
of hyphae, as in the Verticillium disease of potatoes,* or the Wilt 
disease of cotton.t The extraordinary vigour and turgidity of 
sf Pethybridge, G. H. The Verticillium Disease of the Potato, Sci. Proc. 
Roy. Dub. Soe., vol. xv. 1916. ; 
+ Smith, E. F. Wilt Disease of Cotton, etc., Div. Veg. Phys. and Path. 
U.S. Dept. Agr. Bull. 17. 1889. 
