12 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 



have been found. Associated with its presence is usually a 

 large production of tannin, more especially in the two or 

 three outer layers of the cortex. This tannin may be 

 evenly diffused through the cell cavity or occur as small 

 globules in the cell. 



Pinus Sylvestris (Scots Pine). 



The coral-like or nodular mycorhiza of the Scots pine (Fig. 

 5) are so well known, and the description already given for the 

 Mountain pine applies so well to the Scots pine, that only one 

 point of interest in connection with the latter will be mentioned. 

 The main terminal or lateral roots of Scots pine may show 

 what appears to be Endotrophic mycorhiza. In these roots 

 there is a well-defined zone of fungus-containing cells distant a 

 cell or so from the endoderm. The mycelium within these 

 cells is coiled, and from this layer of cells fungal filaments 

 proceed in a radial direction towards the exterior. This 

 radially-penetrating mycelium is much finer than the other, 

 which is irregularly swollen and coiled. In addition to this 

 Endotrophic form the Ectotrophic form is also produced on 

 the same plant, but quite distinct in its location on the plant 

 root-system. 



Fseudotsuga Douglasii (Douglas Fir). 



In neither variety — Oregon or Colorado — is the Douglas 

 fir found to produce mycorhiza readily. Where mycorhiza do 

 occur, however, they are in the form of small clumps similar 

 to the young Scots pine mycorhiza growths, or, more commonly, 

 the rootlet simply becomes enveloped in fungal tissue and 

 appears to the eye rather thicker and more fleshy than is 

 normally the case. These may be the beginning of the clump, 

 but branching has not proceeded on account of the disin- 

 tegration of the tissues of the cortex by the fungus. Where 

 branching has occurred the disintegration of the cortical tissues 

 is not so pronounced. 



Larix Europaea (European Larch). 



The European larch develops mycorhiza rather freely, the 

 form being almost purely Endotrophic (Fig. 6 A). 



