lO TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 



with their common vesicle production, this rather points to 

 them being one and the same fungus. Further, the vesicle re- 

 semblances between the Ectotrophic and this internal mycelium 

 in the older parts of the root, seem to indicate that the internal 

 and external fungus are one and the same. 



This swollen internal mycelium, if it be the beginning of 

 Endotrophic mycorhiza, is very rare in the case of Sitka spruce. 

 It was only found in one locality out of many examined, 

 and from plants which were healthy and vigorous in peat. 

 Ordinary thin mycelium, as already noted, is almost invariably 

 present in the older parts of Sitka spruce roots, more especially 

 in those growing in peat. 



Abies Grandis. 



The presence of the fungus in the case of Abies grandis can 

 be detected by the modification of the rootlets, which become 

 very much swollen near the tip. With the exception of this 

 stunting and thickening, the structure of the mycorhiza is 

 similar to that of spruce. Certain young rootlets in Abies, 

 however, even though enveloped by a fungal sheath, do not 

 become short and thick and arrested in growth, but may be 

 of considerable length. These roots are of a pale colour, and 

 the cortical cells are characterised by their immense develop- 

 ment of intracellular mycelium. The filaments are not of 

 uniform thickness and are without septa. 



Picea Excelsa (Norway Spruce). 

 In all its essentials this resembles Sitka spruce. 



Tsuga Albertiana. 



The condition of the mycorhiza of Tsuga as regards structure 

 and appearance* is similar to that already described for Sitka 

 spruce. In the Tsuga, however, in the main growing roots the 

 only position in which mycelium may be met with is between 

 the cells of the cortex. Internal or external hyphae are absent. 

 It may be described as semi-Ectotrophic. 



2. Pinus Monta?ia Pumilio (Mountain Pine). 



The mycorhiza of the Mountain pine are conspicuous 

 nodular bodies, often over \ in. in diameter, on trees not more 



