KKVIKWS 873 



by means of wooden clamps. Since all of the clamps were not solid, 

 the contacts were strengthened by winding in the spring of 191 5- These 

 experiments were conducted in the experimental garden at Adlisberg, 

 Zurich. Up to the present no indications of grafting have been noted. 



Why then do these small roots not graft? 



Usually such phenomena are noted and passed, but it is of interest 

 to look into the causes. 



The functions of roots are twofold : to supply water and nourishment 

 to the plant during their youth and later to serve as mechanical support 

 to the plant. The absorption of water and salt solutions will be greater, 

 other conditions being equal, the greater the root surface. Hence it is 

 to the advantage of the plant to produce a larger mat of fine roots. On 

 the other hand, there is no gain to the plant by the grafting of these 

 small roots. This holds true in the case of larger roots. 



That absorption roots would not readily graft, due to their elastic 

 -Structure, is conceivable and is also apparent by their cell structure. 

 During the short period of diameter growth of the root tip the new 

 cells are added by cell multiplication at the growing tip just beneath 

 the epidermal layer and from the outside ; consequently grafting becomes 

 impossible or at least very difficult. After the roots have formed a 

 cambium ring and grow by cell division from the inside outward, the 

 grafting becomes possible, the same as branches and stems. Grafting 

 of roots after they are no longer absorption roots is no disadvantage to 

 the tree, but rather strengthens its root system as a mechanical support. 



Just as the radical is geotropic and the stem autotropic, so the cells 

 of the root tips may have repulsive power to keep them separate. This 

 is a problem for plant physiologists. These root conditions are merely 

 mentioned in order to stimulate botanical research along these lines. 



J. V. H. 



Pulpzvood Consumption and Woodpulp Production in IQ18. By 

 F. H. Smith, Forest Service, U. S. Department of Agriculture. Pp. 20. 



The statistics in this compilation are remarkable by their completeness 

 and accuracy, being actual returns from all but one of the 250 estab- 

 lishments in the country concerned in woodpulp consumption. This 

 consumption has for the last three years exceeded five million cords, 

 more than double the consumption of 1899. In value the year's cost 

 of pulpwood exceeded 73 million, more than double that of a decade 

 ago and nearly eight times that of 1899. Spruce is still by far the lead- 

 ing species, and, with balsam added, furnishes over 60 per cent of the 



