ULTRASTRUCTURE OF PTEROSPORA ANDROMEDEA NUTTALL AND SARCODES SANGUINEA TORREY MYCORRHIZAS

Abstract

SUMMARYMycorrhizas of Pterospora andromedea Nuttall and Sarcodes sanguinea Torrey were examined with light and electron microscopes. Both plants were found to have a multi‐layered fungal sheath covering the surface of their roots and a Hartig net surrounding the epidermal cells but not penetrating the underlying cortex. Dolipore septa are present in the fungi of both plants. Individual determinate hyphae enter each epidermal cell through the radial wall which is oriented toward the tip of the root. As they penetrate, the epidermal cell wall appears to invaginate forming a fungal peg. The wall of the peg produces numerous protuberances similar to those found in transfer cells. In the combined fungal‐epidermal cell wall of the fungal peg the two walls do not remain distinct and it is impossible to be certain if both continue to the tip. Eventually, the tip of the fungal peg appears to open and form a mebranous sac, delimited by the epidermal cell plasmalemma, containing granular material with fibrillar inclusions which are approximately the size of microtubules. The relationship of the contents of the membranous sac to the contents of the fungal peg is discussed.