' 





lit.. 5. — Cross-section through an apothecium. The comparatively large size of 

 the asci in relation to the entire fruit body is clearly shown. The epidermis of 

 the needle covering the hvmenuim appears in the bottom of the photograph. 

 June 1956. (X 450; 



SPORULATION 



In 1956 and 1957, very rarely did the hymenium complete its 

 development prior to the initial rupture of the apothecial covering. 

 Since rupturing of the epidermis is the result of the growth and 

 outward development of R. pseudotsugae, examination of apothecia 

 at the time of initial splitting of the epidermis invariably revealed 

 a similar stage of morphological maturity (Fig. 5). Ascospores were 

 beginning to form in the older asci near the centers of apothecia. 

 After this stage, which occurred between May 15 and May 25, nearly 

 a week elapsed before asci and ascospores were mature. 



Both in 1956 and 1957, the first unicellular ascospores were 

 trapped during the fust week of June, at which time the apothecia 

 were considered to be mature. All trapping was by means of vaseline- 

 covered glass slides placed in various places about the infected trees. 



27 



