56 Henderson — Comparative Study of Pyrolaceae and 



in C. umbellate, or C. maculate, and practically every cell be- 

 comes filled with balled-together masses of hyphae. There 

 also occurs on the outside of the epidermis a network of inter- 

 twining hyphae (Fig. 2, 2), forming a sheath 5 from which 

 extend separate filaments F which apparently take the place 

 of root hairs in supplying the root with water. There is a 

 connection between these outer hyphae and those in the epi- 

 dermal cells. These hyphae grow between and around the 

 epidermal cells, until they surround them on all sides, except 

 the interior; so that a tangential section shows epidermal cells 



«mm^? 



^AV 



Fig. 2. Longitudinal sections (X300) of epidermal cells of root tip. 



1. C. maculata 



2. P. rotundifolia 



F = free hyphal filaments, S = sheath. 



separated by a pseudoparenchyma, much like that seen in 

 Monotropa. There is apparently no invasion of any layer 

 beneath the epidermis. Kramar (44) has described all stages 

 of the growth of the mycorhiza. The walls of the epidermal 

 cells first become infested with hyphae forming a pseudoparen- 

 chyma between the cells. Later, when the epidermal cells 

 become full size the hyphae penetrate the cell wall, make direct 

 for the nucleus and begin to form a ball around it. The nucleus 

 finally becomes hypertrophied and lifeless. When this occurs 

 and the cell is packed full of hyphae they penetrate the cell 

 wall again and spread out over the surface. Before this occurs 



