Grossenbacher Radial Growth in Trees. 11 



crown in the pith, rays, and bark yet no radial growth had oc- 

 curred at that point, while, 20 cm. above ground where no starch 

 was present, about 4% of the normal amount of radial growth 

 had occurred. The thickness of the new growth in the trunk 

 increased upward until at 75 cm. above ground a maximum of 

 30% of the normal amount had occurred although no starch was 

 present there. A little starch was present in the main root near 

 the crown but none occurred in the laterals and 110 radial growth 

 had occurred in them. 



Corresponding results were also obtained with the other trees. 

 The starch content and radial growth were found to have in- 

 creased in each case, until, in the tree defoliated 011 August 28, 

 the amounts of both starch and growth were normal. It should 

 be noted, however, in cases where defoliation induced much re- 

 duction of food and growth of the trunks, that a radial growth 

 maximum usually occurred about 75 to 80 cm. above ground, 

 such as given above in detail. The year's growth of full-leaved, 

 young trees was found to be in excess of that occurring in pre- 

 ceding years and their starch content was very high throughout 

 the summer. 



Five young trees of Pinus silvestris were used in similar ex- 

 periments; one being defoliated on each of the following dates: 

 March 20, May 20, June 15, July 1, and August 30. The buds 

 which had been left on the tree defoliated March 20 had burst by 

 May 20, although the needles had not reached full size. On 

 July 1 and 30 some more buds had burst and begun to develop 

 needles. On June 15 small amounts of starch were present in 

 the branches. On August 20 no starch was present and only 

 from 4 to 20% of normal radial growth was found. On Octo- 

 ber 10, when the tree was taken out traces of starch were still 

 present in the base or crown of the trunk but none occurred in 

 the roots. The roots had died and their bark had become loose 

 and infested with nematodes. Brown spots occurred on the 

 bark of the stem and the twigs were being eaten by insects. The 

 new growth was very irregularly distributed over the stem. 

 Around the circumference just above the ground growth varied 

 from none to 8% of the normal thickness and from this point 

 upward the variations were equally as marked. 



In the tree defoliated on May 20 no starch was found during 

 the summer, yet from 10 to 60% of the normal increase in thick 



