78 DISEASES OF CULTIVATED PLANTS 



the plant in obtaining the required amount of water, con- 

 taining salts in solution. From the above statement, it 

 becomes intelligible why, in a particular area, some plants 

 are furnished with mycorhiza and others are not. 



Root-hairs are not present on those rootlets bearing 



FIG. 12. r, ectotropic mycorhiza of larch, nat. size ; 

 2, mycorhiza of same, mag. ; 3, section of root-tip of same, 

 showing mycorhiza surrounding it, highly mag. ; 4, portion of 

 mycelium of same bearing amorphous masses of oxalate of lime, 

 highly mag. ; 5 and 6, endotropic mycorhiza in cells of root of 

 an orchid, Angraecum, highly mag. 



ectotropic mycorhiza, whereas these structures are present 

 on roots of the same plant lacking mycorhiza. 



Ectotropic mycorhiza can be readily found on species of 

 poplars and willows, and on most members of the Cupuli- 

 ferae and Coniferae. 



The hyphae forming ectotropic mycorhiza belong to the 



