Periodical Literature 137 



While, as would be expected, in the leafless condition the dif- 

 ference of absorption of light from the lightest to the severest 

 thinning is relatively small (i : 1.3 : 1.9 : 2.7), in the leafy 

 state the difference becomes greater ( I : 1.6 : 2.4 : 3.8). From 

 the difference of the shade coefficients in the leafless and leafy 

 condition the relation of the size of assimilation apparatus of the 

 average tree appears. This relation appears on the beech areas 

 under comparison as i : 2.6 : 4.7 : 7.7. 



It is now indicated to compare this relation to the actual per- 

 formance in the increment, when it appears that the latter is not 

 proportional, the relation here being i : 1.9 : 3 : 4.7 ; in other 

 words, the large and dense crowns of the open stand do not assi- 

 milate with intensity equal to that of the trees in less open posi- 

 tion, for while the size of crown in the open is 7.7 that of the 

 close stand, the performance is only 4.7 in increment. Here, 

 then, is a numerical demonstration of the fact, which R. Hartig 

 had recognized before. He demonstrated that the crowns of 

 broad-crowned trees in the open could be trimmed of their lower 

 branches to a certain degree without influence on the volume in- 

 crement. Apparently there are in large crowns more numerous 

 but less intensively working "shade" leaves, than in the smaller, 

 more open crowns. 



According to Hartig, open stand produces usually more leaves 

 than are necessary to assimilate the nutrients from the root ; a 

 moderate pruning promotes assimilation of the remaining crown, 

 but it also reduces the transpiration and hence produces heavier 

 wood. 



In further support of these relations the work of the Swedish in- 

 vestigator. Dr. Hesselman, (Zur Kenntniss des Pflanzenlebens 

 schwedischer lyaubwiesen, 1904) is cited, who investigated the rela- 

 tions between assimilation and the loss of shoots in various tree 

 species. He found that some of the notoriously intolerant species — 

 ash, birch, mountain ash — excel by a uniform distribution of assim- 

 ilation throughout the whole crown, while densely- foliaged spe- 

 cies, like maple, alder, hazel, show a great difference of starchy 

 contents in the interior and exterior leaves, the latter assimi- 

 lating more. The light-needing species show in their leaves a 

 nearly uniform anatomical structure, while the shade-enduring 

 show two greatly differentiated types of ' ' shade ' ' and ' ' light ' ' 

 leaves, which latter assimilate much more. 



In consequence the volume increment of the single tree in se- 



