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THE FUNGI WHICH CAUSE PLANT DISEASE 



G. interstitialis (Schl.) Lag.^^-^*- ^^ 



O. Pycnia glandular, numerous mostly epiphyllous. 



I (=Caeoma nitens), hypophyllous, son irregular, confluent; 

 spores orange-red, globose to elliptic, epispore thin, 18^35 x 12-24. 



III. Telia hypophyllous, few, sparse, cinnamon-brown; spores 

 more or less angular, 36-45 x 22-27 fi, pedicel short or wanting. 



AutCEcious, on raspberries and blackberries, wild and cultivated, 

 in United States, Canada, Europe and Asia. 



The pycnial stage appears first in spring giving to the leaves 

 and stems a glandular appearance. About two or three weeks 



Fig. 262. — G. interstitialis, cseoma sorus. After Newcomb. 



later the aicial stage is visible on the lower surface of the leaves; 

 the epidermis soon ruptures and the orange beds of spores show. 

 The pycnia are then fully developed. The affected plants are 

 much stunted and are unproductive but are not killed. The 

 fungous mycelimn is intercellular, growing rapidly into formative 

 tissues and perennating "' in the woody shoots. The knob-like 

 haustoria penetrate the cells and often lie against the nuclei. The 

 mycehum is especially abimdant in the pith near the bundles. 



The seciospores may germinate at once and infect susceptible 

 hosts. The teliospore which is less conspicuous and therefore 

 rarely seen is of the Puccinia type. The telia appear in July 



