Kelley — 146 — Mycotrophy 



with the gelatine ; then growth stopped. This experiment indicated 

 that sugar within the seed was not sufficient to support growth but 

 that the embryo was dependent on an external carbonaceous supply. 

 By further experiment it was found that the orchid fungus could 

 grow "perfectly" on cotton moistened with non-carbonaceous mineral 

 solution, the cellulose being dissolved. These facts fit into a carbon- 

 theory of mycotrophy, and throw further light on the use of sugars 

 in germination of orchid seeds. 



Obligatism in Lower Plants: — The so-called lower plants are 

 yet to be considered. In the hepatics, obligate symbiosis was posited 

 by Chaudhuri (1925) for the Indian liverwort, Marchantia nepalen- 

 sis. This species was found to contain an endophyte characteristically, 

 but sterile thalli were easily raised, developing normally for a time 

 but soon drying up without forming spores. Infested plants both 

 vegetated and reproduced ; from these facts it was concluded that the 

 hepatic cannot develop to maturity without a fungus. Goebel's Or- 

 ganography, 3d Ed., remarks laconically : "This requires further 

 proof". Nicolas (1924), working with Luniilaria cruciata found 

 likewise that fruiting occurred only in infected thalli, the sterile 

 thalli being destitute of mycelium. This observation, together with 

 Golenkin's, suggests the possibility, said Nicolas, that presence of 

 a symbiotic fungus is necessary for fructification. 



Chalaud (1932) considered the fungal endophyte necessary to 

 tuberisation in the Indian hepatic, Sewardiella. Each year the succes- 

 sive gametophytes are infested but the endophyte is checked in the 

 tissues by activity of meristematic cells that are incited to form an im- 

 mune tuber. These facts, thought Chalaud, are in conformity with 

 Bernard's discoveries about orchids ; and he considered Sezvardiclla 

 as the most nearly perfect adaptation of gametophyte to fungus 

 amongst the liverworts, presenting a chart in which Lunularia infec- 

 tion is listed as accidental, Marchantia and Pellia as habitual, and in 

 Fossombronia leading to a tardy tuber-formation and little change 

 in vegetative character. 



As to fern prothalli, Nakai (1933) supposed that uninfected 

 thalli of Cheiroplenria would be sterile or male, implying a need for 

 infection to form archegonia. 



Infection of Lycopods is very general, but we do not know that 

 the symbiosis has ever been claimed as obligate. 



Summary: — From a review of what has been thought and dis- 

 covered about obligate mycotrophy it is evident that there are two 

 view-points in regard to the question, a theoretical and a practical view- 



