Kelley 



170 — 



Mycotrophy 



role, for all the interior cells are cut off from the exterior by a fungal 

 mantle : "Consequently, there is no other way by which the nutritive 

 solutions may pass and provide the roots of Monotropa except the 

 way of the mycelium. This is composed of vegetative filaments of 

 which those that neighbor the epidermis are applied so closely to 

 these cells that diffusion seems not only possible but absolutely exists. 

 Monotropa", said Kamienski, "is thus able to nourish itself by the 

 mediation of this fungus." 



But MacDougal (1900) said that in the Monotropas, vesicles, 

 sporangioids and sporangioles fill the cells, and "probably serve as 

 organs of interchange". Francke (1934) said that infection is 



Fig. 14. — A cell from mycorrhiza of Allium sphaerocephalus showing an 

 arbuscle which is breaking down to form sporangioles {Redrarvn from Gallaud, 

 Rev. gen. Bot., 1905). 



limited to the epidermis, one hypha only penetrating a cell, going to 

 the nucleus where it forms a plasmoptyse, followed by phytophagy 

 in which there is no evidence of excretion. No great changes were 

 observed in the host nucleus. 



In Empetrum (Hasselbaum, 1931) digestion also begins next 

 the nucleus and proceeds outward. During digestion the cell nuclei 

 become amoeboid, its nucleoli are split up and yielded to the plasm as 

 producers of ferment. A distinction between host- and digestion- 

 cells is observable, the cells being of different morphological origin: 

 in the host-cells the fungus forms thick coils of hyphae which are 

 not digested while in the digestion-cells there is a sporangiole mycor- 

 rhiza "destined to digestion". 



In Calluna, Rayner (1927) described intracellular digestion of 

 mycelium. "Throughout the growing season the mycorrhiza cells 

 exhibit active intracellular digestion of mycelium with disappearance 

 of the resulting — and presumably soluble — products. The nearer to 

 the apical meristem, the more rapidly is digestion initiated. Its onset 

 is marked by the usual signs of cell activity — increase in size and 



