TREE ROOTS : THEIR ACTION AND DEVELOPMENT. 21 



case where sufficient speed was used in sectioning and trans- 

 ferring to tiie reagent, the blue colour appeared almost 

 instantaneously round the rootlet, between the cells of the 

 cortex and in the central cylinder. In some cases the addition 

 of hydrogen peroxide was found to be unnecessary, especially 

 in spruce. In roots of as nearly as possible similar age the 

 only oxidation occurred in the central cylinder and in the root- 

 hair region. 



Since in all these species the mycorhizal fungus covers 

 practically the whole rootlet, and often, more especially in the 

 case of spruce and Abies grandis^ forms a mantle over older 

 roots as well, a vastly greater amount of Peroxidase or Oxidase 

 is present in or on the roots of mycorhiza plants than in plants 

 with normal root-hair development. The mycorhizal plant has, 

 therefore, at its disposal a relatively large volume of oxidising 

 agent which may be of the utmost value to the Higher Plant 

 in habitats of deficient aeration and available plant food. It is 

 interesting in this connection to note that peat and bog plants, 

 such as Scirpus, Molinia, and Juncus squarrosus, possess a very 

 large amount of Oxidase in their roots, more especially Molinia. 



EXPLANATION OF FIGURES. 

 (Plates I., II., and III.) 



Fig. I. Sitka spruce root with complete covering of mycelium. 

 Fig. 2. Transverse section of Sitka spruce root with (a) fungal mat, {b) inter- 

 cellular mycelium. 

 Fig. 3. Sitka spruce mycelium*/ 



A. " True " mycorhiza. x 440. 



B. "False" ,, x 440. 



C. Intermediate ,, X440. 



Fig. 4. Mountain pine mycorhiza — rootlets embedded in mycelium. 



Fig. 5. Scots pine — coral-like mycorhiza. 



Fig. 6. European larch : A — transverse section showing {m) intracellular 

 septate, and {m^) intercellular mycelium ; B — longitudinal section. 



Fig. 7- Thuja gigantea — transverse section of root: (a) thickening of 

 cortical cells ; {in) intracellular mycelium ; {ni^) intercellular 

 mycelium. 



Fig. 8. Japanese Umbrella pine — longitudinal section : {a) coiled intra- 

 cellular mycelium ; (fi) terminal vesicle ; (r) nucleus. 



Fig- 9- Japanese Umbrella pine — transverse section : (c) detached vesicle ; 

 {b) granular masses. 



