94 



main trunk wliich tlie wind lias blown down, part of whose roots, however, 

 still remain in the soil, and therefore are still livinj^. Adventitious roots 

 serve the needs of these growths for nutrition. The spruce is certainly the 

 one of all the conifers which can most easily overcome all injuries by develop- 

 ing adventitious organs. 



It also withstands pruning \ery well and can therefore be used ad- 

 vantageously for hedges, only the hedges must be thinned constantly, or 

 they become bare underneath. The ability to form new tips when the old 

 ones have been removed, a characteristic of spruce and Araucaria, is taken 

 advantage of in horticulture, in propagating by cuttings. 



On the other hand, the regeneration ])henomena of the older i)ine are 

 most stable and tixed. The secr)nd type of stilt-growth occurs es[)ecially 

 with this tree, if, in a hilly place, the porous sandy soil slides downwards 

 from the efifects of grading. In the struggle for existcr.ce, how^ever, the 

 pine wdien grown from seed can withstand much better exposure of its roots 

 than spruces and firs ; this is because the roots habitually grow perpendicu- 

 larly into the ground. In the two illustrations which reproduce two examples 

 of Pinus sihestris from the Grunewald (back of Paulsborn) near Berlin, this 

 perpendicular downw^ard growth is shown especially well in the bide roots. . 



Figure 5 show^s two pines standing back of one another with the bases 

 of their trunks about i meter above the ground. The strong main roots send 

 their side branches (arising directly on the underside) into the ground in 

 parallel and perpendicular directions, indicating that the pine roots deeply. 

 The front tree is possibly 60 years old ; the specimen behind it is younger. 

 Figure 6 is taken from another side and shows the side roots starting at 

 right angles from the main branches which spread horizontally from the 

 root crowns. However, in the middle of the stilt appearance, may be dis- 

 tinctly recognized the original main root wdiich as a prop has grown directly 

 into the earth and which endures the chief strain of anchoring the tree in 

 the sandy soil. The tree is still w-ell covered with needles. 



One more important j)b,enomenon must be mentioned in connection with 

 this form of stilt-growth, viz., nianv woody tubers with a dense cf)\'ering of 

 bark grow in rows on the ui)pcr sides of the strong roots. These in figure 7, 

 reproduced natural size, form hemispherical, wart-like prominences up 

 to 1.5 cm. high, with a crater-like depressed centre. They correspond wath 

 the rest of the root in color and bark. 



It is supposed that this arises from an adventitious sprout formation 

 in which the young shoots have died immediately and a heavy scar has been 

 formed. The fact that these growths come only on the upper side lends 

 strength to this supposition. It is well known that when there is this ten- 

 dency toward adventitious growths in trees, the forniation of such buds of 

 all sizes occurs most strongly on the side toward the light (Tilia, Acer). 

 This supposition has not been generally confirmed, as the cross-section (Fig. 

 8) shows. This illustrates a seven years' overgrowth of a centre of disease 

 formed by a homogeneous mass of resin. This resin gall, produced by resin- 



