8i 



drying out on the rock. In figvire 30, we see such a compensatory root which 

 has been developed above the dead tip of the 

 main root A A. The compensatory organ is 

 much stronger and fleshier than the side roots 

 M'hich had been formed earUer. 



The formation of adventitious roots as a 

 resuh of the stimulus of twisting or of injury 

 to the root is constantly utilized technically in 

 the cultivation of trees. In tranplanting seed- 

 lings of forest or fruit trees the main root is 

 either twisted spirally in the hole where it is to 

 be planted or it is shortened about a third. A 

 stronger cutting back is not advisable because 

 •adventitious roots always develop more weakly 

 the older the parts of the axis which are 

 twisted or cut back. 



Fig-. 3. Branch of a spruce 

 root on which a fleshy com- 

 pensatory root has been form- 

 ed above the dead tip. (After 

 Nobbe.) 



b. .Special Cases of Disease. 

 Retrogression in the Cultivation of the Larch. 



As a striking example of the disadvantages developed by the cultivation 

 of plants from mountain climates when grown on the plains, we might con- 

 sider the often noticed retrogression in larch plantations. Kirchner^ 

 mentions, when describing the life history of this forest tree, that it is a true 

 high mountain tree of the European Alpine and Carpathian systems. The 

 natural area of its distribution extends from Dauphine through Switzerland, 

 past Vorarlberg, the Bavarian and Salzburger Alps to the Moravian-Silician 

 depression, and to the Carpathians, up to the hilly country of Southern Po- 

 land. The upper limit for the larch is about 2400 m., the lower one in the 

 Alps 423 m., in the Sicilian mountains about 357 m. AA'hile it thrives in 

 Scotland, Sweden and Norway, it does not grow very well in Middle and 

 Northern Germany or in France. When growing together the spruce usually 

 forces out the larch except in the highest altitudes. When the spruce grows 

 on dry soil it is shorter than the larch. Of all the indigenous conifers the 

 larch needs the most light. It exceeds all conifers and most deciduous trees 

 in its transpiration. Because it is not sensitive to cold, as shown by its 

 natural habitat, it is much more dependent upon the warmth of the summer 

 1.0 make its best growth. It lives in regions where the summer is constantly 

 and uniformly warm, where there is abundant circulation of air and a win- 

 ter's rest of at least four months with a short spring and a rapid transition 

 from spring to summer. Because its leaves come out extremely early, it 

 makes the most of the very short period of growth. 



These statements are based on the observations of numerous specialists 

 and may on this account be acknowledged to be thoroughly reliable. We ob- 



1 Lebensgeschichtc der Bliitenpflanzen Mitteleuropas. 

 Stuttgart, Ulmer 1904. 



Vol. T. Part 



p. 157 



