The importance of genetic factors in bud bursting in Douglas-fir 

 has been recently suggested by Morris, Silen, and Irgens-Moller 

 (38). This would serve to explain the difference between individuals, 

 but variations between buds of the same tree would seem to be due 

 to bud physiological differences or differences in the micro-environ- 

 ment between buds. 



Whatever the cause, buds on an individual tree mature at differ- 

 ent times and the maturation of apothecia is correlated with the 

 stage of bud development in their immediate vicinity. In 1956, at 

 the Camden plantation, apothecia opened a week in advance of the 

 first bud bursting. However, microscopic examination of these apo- 

 thecia disclosed morphologically immature asci and ascospores until 

 the buds were opening. 



Apothecia on the different trees were highly variable in shape 

 and size and, in general, could be assigned to one of two groups. 

 The first included those fructifications ranging from mere flecks to 

 distinct raised pustules 3 to 4 mm. in length. The spores were cast 

 through small openings at the ends of the apothecia. The second 

 group included those extending longitudinally 10 to 15 mm. along 

 the needle length and opening by means of a slit in the epidermal 

 cover, either at the margin of the apothecium or along an indistinct 

 and jagged median suture. No apparent morphological differences 

 in asci and ascospores could be observed within the two groups. The 

 differences suggest morphological strains of R. pseudotsugae in New 

 York plantations. Since the host trees were not genetically uniform 

 this may be a result of host variation; however, the differences were 

 observed on all strains and needle types of the host in the study 

 plots. Wilson and Wilson (70), Peace (40), and Butler and Jones (11) 

 have suggested the possibility of the presence of strains or races of 

 R. pseudotsngae in America, on the basis of their ability to infect 

 the various host strains. Peace (40) states that the fungus varies in 

 fructification, spore shape and size, and probably in pathogenicity. 

 Weistaner (68) in his studies of R. pseudotsngae in Montana re- 

 ported that browning of needles varied from small spots to bands 

 across the width of the lamina. However, he stated that the apo- 

 thecia, asci, and ascospores were the same in each type. 



NEEDLE CASTING 



The casting of needles may begin during the winter, several 

 months before apothecial maturation. Weir (66) reported that in 



24 



