320 USTILAGINEAE. 



side of the leaf. The black spore-masses are formed iu the 

 rind-parenchyma, and sometimes in the pith; they are set free 

 by rupture of the epidermis. 



In autumn the symptoms are different. The plants appear 

 normally developed, and have no coating of conidia ; dark 

 swollen spots, however, appear on the leaves and leaf-petioles, 

 in consequence of the massing of black spore-baUs in the par- 

 enchyma under the epidermis. 



The summer mycelium consists of colourless irregularly 

 branched and slightly septate hyphae occupying the intercellular 



Fig. 175.—Tuburcinia trientalis. Spore- Fig. 176. — Apex of an isolated promy- 



mass genninating ; several promycelia have celium from Fig. 175 ; it carries a whorl of 



been produced and ' are proceeding to form branches, some of which have fused in pairs ; 



whorls of branches. (After Woronin.) all are developing conidia. (After Woronin.) 



spaces of the pith and rind-parenchyma, also the vessels. The 

 hyphae apply themselves closely to the cell-walls, and certain 

 short branched hyphae actually penetrate into the cells. The 

 spore-masses are developed from delicate branched multiseptate 

 filaments of the vegetative mycelium. They begin as two or 

 three little cells round which a coil of hyphae is formed ; the 

 central cells, increasing in number and size, become a ball of 

 dark smooth-coated spores, while the enveloping coil of hyphae 

 disappears. 



The spores germinate during the same autumn, frequently 

 in the position of their formation. A. promycelium is first 

 formed, and on its extremity a circlet of conidia arises ; there- 



