FOLIAGE LEAVES : THE LIGHT-RELATION 



19 



Pig. 12. Two clumps of rcscttes of tlie house leek (Sempervivu?)}), the one to the 

 right showing tiie compact winter condition, the one to the left with rosettes more 

 open after being kept indoors for several days. 



22. Branclied leaves. — Another notuljle feature of foliage 

 leaves, which has something to do with the light-relation, 

 is that on some plants the blatle does not consist of one 

 piece, but is lobed or even Ijrokcii up into separate pieces. 

 When the divisions are distinct they are called leaflets, and 

 every gradation in leaves can be found, from distinct leaf- 

 lets to lobed leaves, toothed leaves, and finally those whose 

 margins are not indented at all (entire). This dift'erence 

 in leaves jirobably has 

 more important rea- 

 sons than the light- 

 relation, hut its sig- 

 nificance may be ob- 

 served in this connec- 

 tion. In those plants 

 whose leaves are un- 

 divided, the leaves 

 generally either di- 

 minish in size toward 

 the to]3 of the stem, 



or the lower ones de- jjo, j3. The leavesof a bellllower (Cto»/OT«!/to), 



velop longer petioles. showing the rusctte arrangement. The lower 



Tt, t-lTiQ P'-isP the erpn petioles are successively longer, carrying then: 



in tnib cabe tne ^eu blades beyond the shadow of the blades above, 



eral outline of the —Alter Keener. 



