264 Plant Physiology 



complished naturally by means of a few fungi, especially 

 Aspergillus niger. 



152. Resins and turpentine.- -A great variety of 

 products of physiological interest and of commercial im- 

 portance are included in the groups commonly called 

 resins and turpentine. They are produced in the cortex 

 and young wood of a variety of plants generally charac- 

 terized by special ducts or canals formed in connection 

 with the conduction of these products. 



The conifers furnish the chief commercial supply, and 

 they constitute an important economic item in many of 

 the coniferous forests of Europe and America. For a long 

 time the balsams, especially the Canada balsam, have been 

 a product of northern forests, whereas the turpentine in- 

 dustry has been best developed in the Southern States. 

 According to Mayr a cubic meter of the splint wood of the 

 standing tree contains approximately the amounts of 

 fresh resins named, of which turpentine oil constitutes a 

 considerable percentage, as follows : - 



It is thus evident that the hemlock, which is poorest in 

 solid resins, contains a very large per cent of the product 

 as turpentine oil. The resins belong to the terpene series, 

 but they occur along with various acids and other com- 



