Kelley — 128 — Mycotrophy 



Vesicles may be inter- or intracellular, or even formed outside the 

 root. Gallaud (1905) regarded the vesicles as "organe de reserve 

 souvent temporaire" (an opinion which Demeter, 1923, shared) ; and 

 he described their formation as almost always terminal: the hypha 

 ceases to grow in length and swells at the extremity while a very 

 dense protoplasm accumulates there and the nucleus multiplies rapidly 

 by division. Groom (1894) thought that the vesicles merely appeared 

 terminal but actually were intercalary, a tip growing into another 

 cell and there forming another or several more vesicles. Similarly, 

 Pyke (1935) said that in Cacao vesicles form in the epidermis and 

 from there a stout hypha grows into cortical cells adjacent ; but 

 Laycock & Dale (1945) state that vesicles were never seen in my- 

 corrhizal roots of Cacao, and arbuscles but rarely ; and they would 

 prefer not to use the term "vesicular-arbuscular" to describe these 

 mycorrhizae. In Vinca, the vesicles form either terminally or inter- 

 calary ; and in age, in addition to a number of nuclei they have great 

 fat vacuoles with protoplasm between them like cross-walls. 



Vesicles were described in detail by Peyronel (1923), who con- 

 sidered them to be reproductive bodies of the endophyte ; and he 

 figured spores within them, — a view that was held by a number of 

 earlier authors {cf. Rives, 1923) ; but "most authors consider them 

 cysts which survive death of the organ and reinfect the new root." 

 Bernard (1911) figured "germination of a vesicle" isolated and 

 placed in a hanging drop; while Johansen (1931) described and 

 figured "spores" (vesicles?) which, he stated, germinate and renew 

 the infection, in certain cacti. In Stapdia variegata, Busich (1913) 

 figured a germinating vesicle. Butler (1939) attempted to grow the 

 fungi from external mycelium and vesicles and, though fine hyaline 

 new hyphae were sometimes obtained, they did not grow extensively. 

 The vesicles of Vitis were figured as thick-walled and containing four 

 rounded bodies like vacuoles (Rives, 1923) ; while in Gossypium 

 they are terminal, round, oval, or irregular (Sabet, 1939). In 

 Lolium (McLennan, 1926), vesicles are oval (65x45 fi), usually 

 terminal but sometimes intercalary and mostly intercellular. At 

 maturity they have thickened walls but later lose their content and 

 collapse. They appear to be "an attempt towards spore formation", 

 while for the higher plant they exist as a "temporary reserve organ". 

 At an early stage they are packed with fat which is later given up 

 to the host plant. 



No vesicles were formed in synthetic mycorrhizae although such 

 occurred in nature (Bouwens, 1937). 



Vesicles are also formed by the endophyte of Conocephalus, both 

 in nature and in culture (Beauverie, 1902; Bergamaschi, 1932): 



