THE MONTHLY BULLETIN. 



273 



Pycnospores and oeciospores are the only forms of spores of the fungus produced 

 during its life on the pine. 



Meanwhile the fungus itself, the fungus plant, has been living in the young stem, 

 sending the delicate threads which make up its body through the young living bark 

 of its victim and taking all its food from that source. For a long time, sometimes 



Fig. 80. — Cronartium ribicola. 



A. "White pine blister rust on young white pine. 



B. Uredinial stage on the underside of Ribes leaf. 



C. Uredinial pustules on Ribes leaf, enlarged. 



D. Teliospores united in form of short threads (Cronartium) 



on the underside of Ribes leaf. 



(From Bureau of Plant Industry Bull. 206.) 



for several years, the host plant, the pine, does not show any external effects of this 

 parasitism. Later the result of the continued irritation caused by the presence of 

 the living parasite in its tissues becomes visible in form of an excessive growth of 

 the affected stem. It begins to thicken locally and finally produces long spindle- 

 shaped swellings which are often thicker at the upper end than below. Both the 

 pycnia and the aecia appear on these swellings. On older stems heavy resin flow 



