292 H. MARSHALL WARD. 



mesophyll are abundance of the usual brown ustilagiuous 

 spores— very like those of Sorosporium, &c. — in dense 

 clusters. 



In the autumn the Trientalis plants are found spotted with 

 black patches. These are due to the densely-clustered brown 

 compacted spores, as before, but no conidia occur now. The 

 pyriform colourless conidium germinates on the leaf surface ; 

 the germinal tube bores its way in, grows to a mycelium which 

 ramifies between the cells, and sends branched haustoria into 

 their cavities. 



At certain points on the mycelium arise lateral branchlets, 

 ■which superficially resemble ascogonia, at least in some cases; 

 these — single or sevei'al together — become enveloped by fine 

 hyphse, and soon present the appearance of a dense grape-like 

 cluster of spores embedded in the interwoven mass of fine 

 hyphse. The investment becomes disorganised as the clusters 

 of spores turn yellow, and then brown, and acquire thick 

 coats. The cluster of spores germinates as a whole, putting 

 out tubes C'^promycelia^') at the end of which the crown of 

 '^sporidia " appear according to the type of Tilletia. These 

 oval sporidia may also ''copulate^' in pairs in the well-known 

 manner; but this often does not occur, and it seems to be an 

 unimportant point, not affecting the future of the sporidia or 

 their progeny at all. Secondary and tertiary sporidia may arise 

 from the primary sporidia by budding. 



After sowing the brown spores on young plants of Trien- 

 talis, still level with the ground or nearly so, the mycelium 

 arises in the seedling, and, as soon as the leaves unfold, pro- 

 duces the white conidia externally and the brown compound 

 spores internally. This is no doubt the best established case 

 of the existence of two generations (producing conidia and 

 spores respectively) that we as yet know of in this group ; it is 

 true, it is not the only case, for we have the same thing in 

 Entyloma.^ Tubercinia also agrees with the others in being 

 antoecious, i. e. in passing its whole life on the same host plant. 

 Woronin is of opinion, however, that " a whole series of hete- 

 1 De Bary, ' Bot. Zeit.,' 1874, p. 81. 



