FOLIAGE LEAVES: THE LIGHT-RELATION. 



19 



YIG. 12. Two clumps of rosettes of the house leek (Sempervivum), the one to the 

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

 open after being kept indoors for several days. 



22. Branched leaves. Another notable feature of foliage 

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

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

 piece, but is lobed or even broken 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 difference 

 in leaves probably has 

 more important rea- 

 sons than the light- 

 relation, but 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 top of the stem, 

 or the lower ones de- FlG 13 The leaveg of a bellflower (Campanula} , 



Velop longer petioles. showing the rosette arrangement. The lower 



Tn this pqP +TiP O-PTI petioles are successively longer, carrying their 



blades beyond the shadow of the blades above. 

 Outline of the After KERNER. 



