CLIMATIC FACTORS 



101 



thinner is the leaf, the narrower the paHsade layer, and the feebler the 

 hgnification. The short-wave ultra-violet light of alpine heights 



Fig. 55. 



-Cross sections through the sun {A) and the shade (S) fronds of Phylliti.-, 

 hybrida. {After Morton.) 



induces, according to Schantz, the dwarf stature and intensive colora- 

 tion of alpine plants. 



Anabolism.—W 2^ii (1925) has given measurements of growth and 

 anabolism of the beech under various light intensities. 



Table 6. — Growth and Leaf Development of Five-year Beech Seedlings 



UNDER Different Light Conditions in Nature 



(After Watt) 



In the type of beech wood studied, the minimum light intensity 

 for the appearance of beech seedlings corresponds with the dominance 

 of Oxalis acetosella and amounts to about }qq of full sunlight. The 

 optimum for young beeches, however, is ^ {, that is, full sunlight. 



The influence of shade in affecting soil moisture and temperature 

 is of great importance in the reproduction of certain trees. Thus 



