212 



MYCOLOGY 



a copious bibliography is one by HowardL. Reed and C. W. CrabiU issued 

 as Technical Bulletin 9 (May, 1915) by the Virgmia Agricultural Experi- 

 ment Station. The 106 pages of text are devoted to a careful considera- 

 tion of all aspects of the disease, which is prevalent throughout the 

 geographic range of the red cedar. The aecia are found on the apple 

 and were originally described as Roestelia pyrata (Schw.) Thaxter, 

 and frequently the apple sUge is known as the Roestelia stage (Fig. 

 81). Infection of the leaves (Fig. 80) and fruit is only possible 

 durmg their undeveloped condition and not all varieties of apple are 

 susceptible. Some are rust free. Such are Early Harvest, Golden 

 Pippin, Winesap, while the badly affected varieties are Grimes Golden, 

 Smokehouse and York Imperial. The aeciospores are dark brown, 



Fig. 82. — Diagram (leit) of aacium (roestelia) of apple rust; right, three EEcio- 

 spores from the cup highly magnified. (After Jones, L. R., and Bartholomew, E. T.. 

 Bull. 257, Agric. Exp. Stat., Univ. Wise. July, ipiS-) 



minutely pitted and almost spheric with thick walls and granular con- 

 tents. The first aecia (Figs. 81 and 82) become mature during the 

 month of July and viable spores are produced in large numbers during 

 this and the following two months (Fig. 83). This is the period of 

 infection of the red cedar, and the mycelium formed from these spores 

 remains dormant in the cedar leaves until the following spring, when 

 the cedar apple (Fig. 76), or gall, is formed out of the parenchyma 

 of the red cedar leaf (Fig. 161). Into the gall a vascular strand extends. 

 The surface of the galls becomes papillate and in May these papillae 

 enlarge into gelatinous horns, or teliosori (Fig. 77), made up of the 

 agglutinated stalks of numerous teliospores (Fig. 77), which are two- 

 celled and measure 46 to 63/^ by 15 to 20/i (Fig. 78). These telio- 



