565 



and, on tliis account, chiefly autumn wood is formed. If much material is 

 present, i. e., the annual ring is broad, a strong autumn wood ring has been 

 developed (v. Mohl). In deciduous trees in which the development of the 

 root body is continued until the next year and, in fact, as has been shown 

 above, often does not end before the blossoming time of the next growth, 

 all differentiations are weaker and the boundaries of the annual rmgs less 

 distinct. .Since it becomes spring in the layers of the soil only after it has 

 Ijecome summer above ground, spring wood is always formed in the roots. 

 In the further advance of the annual ring, its development depends on the 

 degree and continuance of the soil warmth and dryness. If a year has a 

 long dry period, autumn wood is formed. If this is not the case, develop- 

 ment is limited to spring wood, with only a weak beginning of autumn wood 

 formation. Hence the porous structure of the slender ringed root. 



By briefly repeating what has already been stated, we can summarize 

 the dift'erence between root and trunk in deciduous trees, since first the 

 annual rings in the root are much more slender than the corresponding ones 

 of the trunk and, second, in the constant development of porous spring 

 wood, these slender layers are predominantly porous. In conifers the same 

 difference is found between trunk and root, so far as the slenderness of the 

 annual rings is concerned and, in the same way, the thicker the annual 

 ring the more the autumn wood decreases in proportion to spring wood. 

 The wood cells are everywhere longer and wider and their walls thinner 

 in the roots than in corresponding parts of the trunk. 



Therefore, greater attention should be paid to the freezing of the roots 

 because in this is found the explanation of numerous cases of summer 

 death in indi\idual trees and groups among those of the same age and of 

 the same species. Trees with frozen roots, like healthy ones, usually 

 sprout in the spring and often develop normal shoots, even if they bear as 

 a rule smaller leaves. Not until summer, but then advancing especially 

 quickly, does a yellowing of the leaves begin and also a drying of the twigs. 

 The water supply of the trunk is then used up by the transpiration of the 

 leaves. 



Even in localities and varieties wdien no injury of the aerial axis is to 

 be feared from winter frosts, fruit trees in pots should be brought into 

 protected places, because of the sensitiveness of the roots and, in open land 

 cultures, the natural protection from foliage and snow should not only be 

 left but, if possible, increased. In planting tree plantations, it will only be 

 possible to carry out the otherwise advantageous autumn planting without 

 danger if absolutely hardy trees are used or the planting takes place so 

 early in the autumn that, preliminary thorough puddling being taken for 

 granted, rooting and a close packing in of the roots in the earth may be 

 assumed. DuhameT observed that a formation of fibrous roots can take 

 place even in winter. This was later substantiated by Lindley. In less 



De.s semis et plantations des aibres, p. 155. 



