Table ^.-Influence of time on germination of urediniospores at cool, moderate, and warm temperatures 



Germination Mean germ tube length 



jjj^g Temperature (degrees C.) Temperature (degrees C.) 



(hours) 8 18 28 8 18 "28" 



Percent Microns 



3 86 96 67 53 157 64 



6 .95 94 87 135 270 84 



12 93 96 76 311 376 109 



24 99 98 83 420 520 116 



48 96 99 88 450 541 124 



Effects of Temperature on Germination 



Method.— V iQsh. telia from inoculated 

 comandra in a greenhouse were placed in petri-plate 

 moist chambers maintained at various temperatures, 

 to an accuracy of about ±0.5° C. Excised telia were 

 attached vertically by their bases on 2 percent water 

 agar on the insides of plate covers. When teliospores 

 germinated, basidiospores fell onto plates containing 

 2 percent water agar (adjusted with HCl to pH 

 approximately 2.0 to prevent germination of the 

 basidiospores, which makes counting difficult). After 

 3, 6, 12, 24, 48, and 72 hours, the covers were 

 rotated by hand so that time of spore casting could 

 also be determined. Teliospore germination was evalu- 

 ated by counting the basidiospores cast from whole 

 teha. 



/?esu/rs. -Excellent casts of basidiospores 

 were produced at temperatures of 13° to 23° C; 

 casts were fair but slower at 8° C, and poor at 6° 

 and 24° C. (fig. 8). No basidiospores were cast at 3° 

 or 25.5° C. and higher. At 25.5° C, basidia formed 

 but no basidiospores developed. At 28° and 30.5° C, 

 not even basidia formed. Comparisons by Duncan's 

 New Multiple Range Test (Duncan 1955) at the 0.01 

 level indicated that the excellent casts at temper- 

 atures 13° to 23° C. were not significantly different 

 from each other at 12 and 24 hours, but were better 

 than casts at other temperatures and continued to be 

 greater throughout tlie remainder of the 72-hour 

 incubation period. In other similar tests the relative 

 position of the maximum casts varied between 13° 

 and 22° C, but at 25° C. and higher there were never 



any casts, and longer incubations were always 

 required at temperatures less than 13° C. These 

 results are a refinement over an early report by Mains 

 (1916). He reported no germination at 10° and 30° 

 C, fair germination at 18° C, and good germination 

 at 24° C. 



Figure 7. -Telia of C. comandrac on comandra 

 leaves (X 9). Telia are common on both 

 upper and lower surfaces of leaves and 

 on stems of Comandra umbellata ssp. 

 pallida. 



7 



