10 20 30 40 50 60 70 



TIME IN HOURS 



Figure 8.~Germination response of teliospores 

 to several temperatures. Each curve rep- 

 resents the cumulative mean from 10 

 telia. 



Figure 9.-Clock-drive unit that automatically 

 rotates cover of large petri plate. When 

 telia are attached to the cover, basidio- 

 spores are cast onto the stationary bot- 

 tom of the petri plate so as to reveal by 

 their position when casting occurred. 



Effects of Freezing and Heating on Viability 



The effect of freezing temperatures on via- 

 bility of teliospores was tested under laboratory con- 

 ditions. Fresh telia produced from greenhouse inocu- 

 lations were excised from comandra leaves. These 

 telia were then subjected to below-freezing temper- 

 atures such as occur during mild to severe frosts in 

 the field (table 5). Each treatment was replicated 

 with nine teUa of equal size for each temperature. 

 A'fter exposure, telia were incubated at 18° C. for 72 

 hours in moist chambers and basidiospores cast were 

 counted. 



As shown in table 5, freezing reduces the 

 ability of telia to cast basidiospores. This effect 

 occurred whether or not the process of germination 

 had already begun at the time of freezing; basidio- 

 spore casts were suppressed in telia frozen immedi- 

 ately after removal from comandra leaves and also in 

 telia previously incubated under conditions favorable 

 for germination. Suppression increased with increas- 

 ing severity of freezing treatment. 



Fresh C. comandrae telia from Cache 

 National Forest were also subjected to warm temper- 

 atures to determine if heat might suppress subsequent 

 casting of basidiospores as it has been shown to do in 

 C. ribicola (Van Arsdel et al. 1956). All telia in each 

 trial were of nearly equal size, and no previous germi- 

 nation had occurred. Five telia were used for each 

 treatment. Both dry teUa (placed in paper bags) and 

 telia in moist chambers were exposed to heat treat- 

 ments (table 6). As in earUer tests, telia were then 

 placed in moist chambers at 18° C. for 72 hours and 

 basidiospores cast were counted. 



Heat suppressed the abihty of teliospores to 

 germinate (table 6) but rather long periods of expo- 

 sure to warm temperatures were necessary. It would 

 seem unlikely that in pine areas of the Rocky Mountain 

 States warm temperatures would last long enough to 

 alter teUospore germination. 



Influence of Light on Germination 



To test the influence of light, freshly excised 

 telia from inoculated comandra were stuck to the 

 inside covers of petri plates, as described earlier for 

 temperature studies, and were placed in natural or 

 artificial light or in darkness. The covers were contin- 



8 



