320 



USTILAGINEAE. 



side of the leaf. The black spore-masses are formed in 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-balls in the par- 

 enchyma under the epidermis. 



The summer mycelium consists of colourless irregularly 

 branched and slightly septate liyphae occupying the intercellular 



FIG. 175. Tuburcinia trientalis. Spore- 

 mass germinating ; several promycelia have 

 been produced and are proceeding to furni 

 whorls of branches. (After Woronin.) 



FIG. 176. Apex of an isolated promy- 

 celium from Fig. 175 ; it carries a whorl of 

 branches, some of which have fused in pairs ; 

 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 promyceliuni is first 

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



