Fig. 19. — Thin intercellular hyphae near the outer margin of 



the needle 49 



Fig. 20. — Longitudinal view of the mesophyll just below the 



lower epidermis 49 



Fig. 21. — Cross-section of a needle showing mass of hyphae 



under the stomata 50 



Fig. 22. — Individual differences in susceptibility to 



R. pseudotsugae 57 



