562 



frost injury, on the one hand, and tlic prcxious nutrient eonthtion of the 

 tree, on the otlicr. to^ctlicr witli a greater or lesser ease of adventitious 

 hud formation, oharaeteristie of each \ariety. call forth different compen- 

 satory shoots in different cases. The more luxuriantly a variety grows, 

 the more it inclines to the formation of "lower buds." as can he observed 

 frec|uently by the breaking of eyes on the main stem. 



In gra}ie\ines. regeneration takes place from the lateral buds if frost 

 has killed the main ones. This depends greatly on the time of the frost 

 action. If the death of the main bud takes place so earl\- in the \ear that 

 it has used but \ ei"y little reser\ e material in. its elongation, then fre(|uently 

 the reser\e material still jiresent in the \ine is sufiicicnt to strengthen the 

 lateral buds so that blossom buds can still be set. If, however, the main 

 bud dies from a frost in May. strong shoots can dexelop. to be sure, from 

 the lateral buds, but without setting blossoms. These shoots become fertile 

 only in the next year. 



Fki-:i-:zinc; of Koots. 



Not infreciuently. especially in wet places after open winters, the roots 

 of very different: woody plants are found to ha\e been frozen while the 

 aerial, axillary parts have remained ali\e. This phenomenon i^ exjilained 

 by the fact that the wood of the roots is softer and more porous than that 

 of the trunk. The softness is due, on the one hand, to the fact that, at the 

 time when the cold penetrated deepest into the soil, the growth of the root 

 had not entirely stop])ed ; therefore the frost attacked still )<)ung, unthick- 

 ened elements. On the other hand, howe\er, the already matured elements 

 of the wood body are not so thick-walled as the corresponding parts of the 

 aerial, axillary body. This, is uni\ersall\- true w ithout taking into consid- 

 eration the nutriment and water content of the soil. That the degree of 

 luxuriant development will also exert an influence on the sensitiveness to 

 frost cannot be denied, but this influence, according to \ . Mohl's investiga- 

 tions', manifests itself differently. 



A consideration of the annual range of temi)erature will gi\e the 

 necessary explanation in regard to the first point, the action of the frost 

 wave on roots not yd dormant. 



It should be noted in advance that measurements of the tree's tem- 

 I)erature prove the dependence of this temperature in the tree toj) on the 

 fluctuation in the atmospheric warmth, while the temperature of the trunk, 

 especially at the l)ase and in thick barked varieties, is \ery considerably 

 influenced b}- the warmth of the soil-, since the water, necessarily rising to 



1 V. Mohl, I<]iiiise anatomi.sctip unci ))hysiok)g:i.sche Hemerkunsen iibcr das iio\y. 

 der Baumwurzeln. Bot. Zoit. 3 862, Nos. 29, 33, 34, ff. 



- Breitenlohner and Boehm (Sitz. d. Kais. Akad. d. Wis.s. zu Wcin, May 17th, 

 1877) found that under usual eondition.s the temperature of the lower part of the 

 stem is entirely influenced by soil temperature, but if transpiration is arrested, the 

 temperature of the tree depends entirely on the air temperature. 



