Tree Mycorrhiza. 215 



early stage of decay, (2) an abundance of intertwining hyphae, 

 many of which are attached to roots. 



Close observation is necessary before rootlets can be detected 

 that are not in a mycorrhizal condition. The mycorrhiza of 

 hornbeam and sweet chestnut (figs. 2 and 3) exhibit respectively 

 characteristics similar to those of fig. i, but there are small 

 differences of detail. 



A clump of moss is a most favourable nidus for the germination 

 of birch seeds and those germinating naturally under such 

 circumstances, as great numbers do, are found to develop 

 mycorrhiza at a very early period of their existence, \-iz. before 

 the cotvledons have ceased to function, while the stem is yet 

 little more than half an inch in height, and before the radicle 

 has passed through the lowest layer of the moss carpet. 



The birch seedling illustrated in fig. 4 was collected on 

 13th October, 1923. Its trilobed, lower leaf indicates the first 

 year of growth and as it germinated most probably in the pre- 

 Wous April it is probablv six months old. The whole of the root 

 system is mvcorrhizal. and in this case is of two kinds, one of a 

 dark gray colour and the other of a white sHghtly shaggy appear- 

 ance which we associate with the fly agaric, Amanita muscaria. 



Three to four states of mycorrhiza, differing in form, size, 

 texture and colour, occur on the same species of tree and quite 

 frequentlv two forms appear on an identical root-branch. 



The most common mvcorrhiza of beech is dark brown in 

 colour and wax-like in appearance. These characteristics give 

 no clue to its fungal origin. Besides the above, a yellow and a 

 white m3'corrhiza are frequentl}^ met \nth on the roots of this 

 tree. The latter being shaggy, it is possible, on examining it in 

 a tube of water, to see with a pocket lens of low magnifying 

 power loose hyphae extending from its surface in all directions. 

 These hyphae come into contact with decaying leaves to which 

 they adhere, but in the case of the wax-hke form actual contact 

 with the humus matrix is restricted considerably. 



The mvcorrhizal roots of Pi nits sylvestris are coralloid, that 

 is, the branches of the root are short, closely clustered, and being 

 pinkish in colour somewhat resemble coral. The branches are 

 mostly furcate at the extremities, and average 4 mm. in length 

 and 0-5 mm. in diameter. 



In attempting to establish the mycehal connection between 

 mycorrhiza and the sporophore of a Basidiomycete (fig. 5) 

 frequent failure results. A mycehum may break and when it 

 is white and is mixed with many similar ones it is scarcely 

 possible to be sure of catching up the right thread. A case has 

 been recorded of following up a coloured mycehum for a distance 

 of 54 deem. = 17-7 ft. (2). In a great majority of cases the 



