2i6 Transactioyis British Mycological Society. 



mycorrhiza is only one to three inches from the toadstool with 

 which it is associated. 



A method that has given satisfactory results is that of cutting 

 a circle through the surrounding leaves and other debris to a 

 depth of three inches at a radius of six inches from the stipe of 

 the sporophore, and then, working from opposite points with 

 the fingers of both hands until the whole mass can be lifted from 

 its surroundings. Such a mass with the base of the stipe attached 

 can be carried without danger of disturbing the roots within. 

 Having severed a number of roots during the cutting of the 

 circle it is possible to trace one that comes from near the centre. 

 By carefully removing the material attached to the root it is 

 possible to demonstrate the connection, by means of a mycelium, 

 between the mycorrhiza and toadstool. 



The stages in the formation of mycorrhiza from a normal root 

 have not been seen, but observation of roots after heavy rain, 

 which followed dry weather, has been sufficient to enable the 

 writer to conclude that new rootlets followed by a complete 

 change to mycorrhiza have developed within ten days. 



Peyronel(3) has recorded the association of a large number 

 of Basidiomycetes with the roots of forest trees. His list includes 

 for Beech, Cortinarius proteiis, Boletus chryseriteron, B. cyanes- 

 cens, Scleroderma vulgare, Amanitopsis vaginata, Lactarius sub- 

 dulcis; for Sweet Chestnut, Amanita rubescens, Russula lepida, 

 R. rubra, Scleroderma vulgare; and for Birch, Tricholoma flavo- 

 brunneum, Amanitopsis vaginata, Amanita muscaria, Boletus 

 scaber, B. radicans. Scleroderma vulgare. 



A transverse section of the dark brown mycorrhiza of birch 

 (fig. 6) has a diameter of 0*35 mm. It exhibits a series of three 

 concentric circles the outer of which, the mantle, a consists of 

 hyphae so closely compact that they form a plectenchyma similar 

 to that of the upper surface of some foliose lichens. Within the 

 mantle are the cortical tissue b, c, d and the central axis e of the 

 birch root. The epidermis appears crushed and root hairs cannot 

 be traced. The outer cells of the cortex are elongated radially. 

 Hyphae, that have, by the secretion of an enzyme, dissolved 

 the middle lamella may be seen between the cortical cells to have 

 entered the cortex to a depth of three to four cells. Occasionally 

 one of the hyphae is seen to have penetrated a cell-wall and to 

 have developed a vesicle at its extremity (fig. ya). Such a vesicle 

 is of the nature of a haustorium but the fact that this develop- 

 ment is so rarely met with prevents one from basing any theory 

 upon its presence. It is sufficient for our present purpose to note 

 that haustoria do occur. 



The object of these notes, which for the most part are based 

 on field observations, is to suggest that investigation following 



