Kelley — 152 — Mycotrophy 



significance of the host-cell is an exclusive use for the fungus which 

 grows there purely as a parasite, injures the protoplasm, forms 

 "closed" organs which apparently serve to overwinter the plant. It 

 was adopted by Kusano (l^^O who said that the fungus, although 

 it acts as a parasite at times, becomes a victim of the orchid so that the 

 reciprocal exchange is not equal, for "Gastrodia is parasitic on the 

 fungus". And Cortesi (1912) believed the relation between fungus 

 and orchid is a case of helotism in which the fungus plays a subor- 

 dinate role. The orchid supports and nourishes the endophyte so long 

 as its presence is beneficial but it finally kills the fungus when flower- 

 ing and seed-production time arrives. 



Prat (1934) came to the same conclusion about Taxus canaden- 

 sis. Symbiosis, he said, is scarcely the term to be used but disease, 

 for the invading fungus is limited by the host; and thus the tree 

 becomes a parasite on its parasite ! For Empetriim, Hasselbaum 

 (1931) concluded that there is no question of a mutual symbiosis, 

 but rather an attraction and destruction of the endophyte ; and Fraser 

 (1931) regarded two species of Lobelia studied as parasitic upon 

 their mycorrhizal fungus. For Vinca, Demeter (1923) saw an ad- 

 vantage to the host plant, according to Frank's concept, in myco- 

 phagy by which the host makes a certain gain in N ; but he did not 

 regard the symbiosis as ideal since the host-plant may be badly in- 

 jured. Besides, under cultural conditions the fungus-free plants 

 made decidedly better growth than the infected, indicating the my- 

 corrhizal relation was more of a parasitism. 



Romellian Hypothesis: — In contrast to mycophagy is Romell's 

 (1939) hypothesis: that "the obligate mycorrhizal fungi associated to 

 conifers are not saprophytes decomposing soil organic matter, and 

 that they are energetically parasites on their host trees." MacDougal 

 & Dufrenoy (1944) take an opposite view-point, stating that "The 

 absorption of inorganic phosphorus from the soil by the fungus and 

 the stages of its metabolism terminating in the stele of the root, identi- 

 fiable origination in hyphae and translocation of auxin, vitamins and 

 amino compounds to the root tissues, together with the capacity of 

 isolated segments of mycorrhizal roots to survive and grow, like a 

 chlorophylless plant, establishes the non-parasitic character of the 

 fungus." Bjorkman (1944), furthermore, found that on so treat- 

 ing pine seedlings that they ceased to form carbohydrate in the root, 

 the fungus did not become a parasite : it simply ceased to "attack" 

 the root. 



