BEGINNING OF THE STRUGGLE. 



53 



ill height and spread of crown. Growth in this way 

 was going on unchecked among the young trees be- 

 fore the crowns met, but now only the upward-grow- 

 ing branches can develop freely. The leaves at the 

 ends of the side branches have now less room and, above 

 all, less light, for they are crowded and thrust aside by 

 those of the other trees. Very often they are bruised 

 by thrashing against 

 their neighbors when 

 the wind blows, or 



even broken off while 

 still in the bud. 

 Leaves exposed to 

 such dangers are un- 

 healthy. They tran- 

 spire less than the 

 healthy, undisturbed 

 leaves of the upper 

 part of the crown, 

 and more and more 

 of the undigested 

 food from the roots 

 goes to the stronger 

 leaves at the top 

 as the assimilating 

 power of the side 

 leaves dwindles with the loss of light. The young 

 branches share the fortunes of their leaves and are vigor- 

 ous or sickly according to the condition of the latter. For 

 this reason the growth of the tops increases, while that of 

 the lower lateral branches, as the tops cover them with a 

 deeper and deeper shade, becomes less and less. Gradu- 

 ally it ceases altogether, and the branches perish. This 



Fm. 50. — Small saijlings of White Pine grow- 

 ing thickly together. Milford, Pa. The 

 space betsveeu each cluster or whorl of side 

 branches marks one year's growth. These 

 young Pines are beginning to grow rapidly 

 in height because they can no longer spread 

 at the sides. 



