89 



The most tender tissue of the tree is in the roots. Thus in case 

 of the tree frozen July 2, 1913 (Table 24) when the tissue above 

 ground is most tender, the roots were injured in the cambium at -3.5° 

 C, and severely injured in cambium, cortex and sap wood at -4.5° 

 C. Goeppert 1 found that the roots of hardy plants kill at a tem- 

 perature of from -10° to -15°. A study of the killing temperatures 

 of roots of various fruit trees has been made at this station. In the 

 summer there is not so large a difference between the killing tempera- 

 ture of roots and other tissue. However, the roots do not seem to 

 develop as great maturity as the tissue above ground. The following 

 table shows the results with freezing the roots of trees in summer and 

 winter seasons: 



Table 30. Showing Killing Temperature of Apple, Peach, 

 Plum and Pear Roots. 



Kinds of Roots 



Tem- 

 pera- 

 ture 



Results 



Two-year Ben Davis 

 apple roots 



Seedling two-year old 

 apple stock roots.. . . 



Two-year Ben Davis 

 apple roots 



Seedling apple stock 

 roots 



Seedling apple stock 

 roots 



Two-ye.ar Ben Davis 

 apple roots 



Two-year Ben Davis 

 apple roots 



Seedling apple stock 

 roots from basement 

 since December 

 20th 



Seedling apple stock 

 rootsf rom basement 

 since December 

 20th 



Apple stock buried S 

 in. below surface 

 outside since Jan. 

 8th 



June 23/13 



June 24,'13 

 June 25,'13 

 Aug. 20,'12 



Aug. 22/12 

 Dec. 7/12 

 Dec. 7/12 



Jan. 13/13 



Jan. 17/13 



Mar. 8/13 



-S 

 -3 

 -6 



-5 

 -6.5 



-4 



-9 



-10 



Cambium only injured in larger 

 roots. Cortex also injured in 

 roots yi in. in diameter. In 2 out 

 of 4 cases, crown uninjured. In 

 other 2 cases there was slight 

 injury to cambium at crown. 



No injury at all 



No injury in roots above % in. in 

 diameter. Wood just above 

 crown was injured in cambium. 



Cortex and cambium region all 

 dead. 



Cortex and cambium injured, but 

 less severely than above. 



Cortex, cambium and wood in- 

 jured. 



One small root injured. 



Injury confined to cortex region. 



Injury slight and confined to cortex 

 region. 



One root browned and the other 

 not injured 



iTTeber die W&rmeentwickelung In dem Pflanzen, etc., book, 1830. (Bibl. No. 44). 



