FOLIAGE LEAVES: THE LIGHT-RELATION 
19 
FIG. 12. Two clumps of rosettes of the house leek (Sempervimim\ 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 leaves of a bellflower (Campanula ^ 
Velop longer petioles. showing the rosette arrangement. The lower 
Tn tlii PPSP +ViP o-Pn petioles are successively longer, carrying their 
blades beyond the shadow of the blades above, 
eral Outline of the After KEENER. 
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