■4 



r 



M 



Fig. 9. — Typical early germination stage of the ascospore. The germ tube is 

 evident from the reverse side, looking through the dark cell of the spore. In this 

 spore the hyaline cell remains distended, since the spore was free in the apo- 

 thecium. July 1956. (X 1100) 



but further growth into a branched, septate mycelium characteristic 

 of R. pseudotsugae was not observed. 



Spore ejection from the ascus was demonstrated by the procedure 

 used by Weir (65) for Hypoderma deformans Weir. Portions of 

 moist needles with fresh mature apothecia were placed in the depres- 

 sions of culture slides. The slides were placed on moist filter paper 

 in petri plate halves, covered, and allowed to dry slowly. After 24 

 hours spores were observed on and around the needle, up to 1.5 mm. 



from the apothecial margins. Weir (65) reported that in H. defor- 

 mans the hygroscopic movements of the apothecial lips forced spores 



from asci. In this study, Rhabdocline pseudotsugae spores were 



actively ejected from apothecia whose epidermal covers had been 



carefully removed. 



Douglas-fir needles, heavily infected by R. pseudotsugae, are 



readily cast after ascospore discharge and, at times, may fall before 



32 



