I'LANT STL;])1ES 



i\n\ aiiKiimt lit' work nil active leaf cau do will dejiend in 

 part u})oii the amount of sui'faee it exposes. 



receive 



'Jill-; LII + IIT-KKLATKJK 



12. The general relation. — The ortliuary position of the 

 foliage leaf is more or less horizontal. This I'liables it to 

 the direct rays of light iqjon its upjier surface. lu 



this way miu'c rays of 

 light strike the leaf sui'- 

 face than if it stood olj- 

 liquely or on edge. It is 

 often said that leaf blades 

 arc so directed that the 

 flat surface is at right 

 angles to the incident 

 rays of light. "While this 

 may be true of horizon- 

 tal leaves in a general 

 wa}', tlie observation of 

 almost an)' plant A\ill 

 show that it is a vi^ry 

 general statement, to 

 wliich tliere arc numerous 

 exceptions (sec l''ig. 1). 

 Loaves must ]>v arranged 

 to receive as much light 

 as possilile to help in 

 their work, but too much 

 light will destroy tlie 

 green sul)stanco [cJiloru- 



Jiu. 1. ■rm- icavrs (It tills pkint (y'Vr«x) are pJ/l/U). which is I'SSCntial 

 in general lioiizontal, but it will be bi'imi i,-, ii ,,. ,.i_ rni , t- , 



,, t^ ,. , ,■ , , , to tJie woiiv. i lie ad ust- 



tiiat the lower onea arc clneeled down- _ ^ 



ward, and tliat tlie li'aves li.Tome, more mcilt to light, therefore, 



horizonlai n» Ibe .bni i„ aseended. It J^ .^ dclll^alc one, for 

 will also ),c sr.ii tliat llir Iravrs aiv .so 



luoad lliatlliiTe arc few verlical rows. there must be just CUOUgll 



