42 



Journal of Agricultural Research voi. xxii. No. 



Although several seasons' observations had shown no noticeable loss 

 through winter frost heaving of i-o western white pine transplanted in 

 April and in early May, it was found in the spring of 1918 that of 2,922 

 i-i white pine transplanted June 15, 19 17, in connection with another 

 experiment, 1,152, or 39.4 per cent, were heaved out during the late 

 fall, winter, and early spring of 19 17-18. This is nearly as heavy a loss 



Ma(/9 May20 Mat/30 Junel2 JunelS JuneJO Jultjl^ 



Time of Transplanfina 



Apr 24 May I 



Fig. 6.— Number of lateral rootlets on seedlings transplanted at different dates. 



as had previously been recorded for fall transplanting. However, an 

 unprecedented snowless period in December probably contributed to 

 produce this result. A greater susceptibility to frost heaving on the 

 part of late spring and summer transplants is the natural result of the 

 poorer root development just referred to. The plant must rebuild its 

 entire root system late in the season and so has a relatively poor anchor- 

 age when the frost comes. Furthermore, Cannon * has found that the 



1 Cannon, William Austin, root habits oP desert plants. 96 p., x7 fig., 23 pi. Washington, D. C„ 

 igii. (Carnegie Inst. Wash. Pub. no. 131.) 



