Relation oj Funi];i to other Or (danisms. A . Lor rain Smith. 2^ 



destroys the contents of the cells while in the innermost cells 

 the hyph.:e are digested by the host. 



l^ndotropliic m\corrhiza is a \ery wide spread phenomenon 

 and appears in many plants botli in JMonocotyledons and 

 Dicotyledons. Gallaud* who studied thoroughly this type 

 held that the hyphr.e were attracted chemically by the roots; 

 they penetrate the outer cells of the cortex and, in the deeper 

 seated cells, they form branching haustoria termed 

 " arbuscules," while on the tips of the hyplve swollen 

 vesicles are formed whicii function as reserve organs or 

 may become reproductive bodies. In some cases only 

 occasional cells are entered by the fungus; in others every 

 cell of the cortex may be infected ; the fungus never penetrates 

 the vascular cylinder nor does it invade chlorophyll cells. 

 The hyphie may be coiled rtnmd the nucleus of the cell or 

 may have no relation with it; they pass from cell to cell 

 but they do not destroy the middle lamellae, nor split the 

 cells apart as in ectotrophic mycorrhiza. 



A wonderful instance of mycorrhiza association has been 

 worked out by Miss Raynerf in Calluna and some other 

 Ericaceae. She foimd that the seeds already harboured the 

 mycelium of the fungus in the testa so that as the seed 

 germinated, the luphie infected the seedling and formed 

 mycorrhiza on the roots; without such infection all growth 

 ceased and the seedling died off. Infection may begin at the 

 tip of the root bv hyph,a3 finding their way into the cells in 

 which is formed a tangle of fine filaments. The fungus 

 eventually spreads (jver and within the whole plant — root, 

 stem, branches and leaves — so that when the seeds are formed 

 it is again present. It penetrates continually from the open 

 into any part of the host with ease and, within certain cells, 

 it forms coils of extremely attenuated filaments which are then 

 digested and used by the host. It even invades the 

 chlorophyll cells and though it is digested, the chloroplasts 

 and contents also suffer disintegration. 



From pure cultures of the fungus evidence was obtained 

 that it belonged to the genus Phoma or to Phyllosticta. 



In discussing the biological relations between the host and 

 the hyphai of endophytic mvcorrhiza, Cyril West:|: 

 recognizes three different relationships : — 



I. — A real symbiosis: (A) the host provides habitation, 

 and carbohydrates (especially starch) ; (B) the fungus yields 

 up to the higher plants mineral salts absorbed from the soil, 

 and proteids converted bv it from the humus. The fungus 

 mav also fix nitrogen from the air to the benefit of the host 

 plant. 



* Gallauf], 'o_T. f Rayner, '15. + West, '17. 



