FOLIAGE LEAVES : THE LIGHT-RELATION 
17 
smaller and less horizontal toward the apex of the stem 
(see Figs. 10, 13). The common shepherd's purse and the 
mullein may be taken as illustrations. By this arrange- 
ment all the leaves are very 
completely exposed to the 
light. 
21. The rosette habit. 
The habit of producing a 
cluster or rosette of leaves 
at the base of the stem is 
called the rosette habit. 
Often this rosette of leaves 
at the base, frequently lying 
flat on the ground or on the 
rocks, includes the only fo- 
liage leaves the plant pro- 
duces. It is evident that a 
rosette, in which the leaves 
must overlap one another 
more or less, is not a very 
favorable light arrange- 
ment, and therefore it must 
be that something is being 
provided for besides the 
light-relation (see Figs. 11, 
12, 13). What this is will 
appear later, but even in 
this comparatively unfavorable light arrangement, there is 
evident adjustment to secure the most light possible under 
the circumstances. The lowest leaves of the rosette are 
the longest, and the upper (or inner) ones become gradu- 
ally shorter, so that all the leaves have at least a part 
of the surface exposed to light. The overlapped base of 
such leaves is not expanded as much as the exposed apex, 
and hence they are mostly narrowed at the base and broad 
at the apex. This narrowing at the base is sometimes 
FIG. 10. A plant (Echeveria) with fleshy 
leaves, showing large horizontal ones 
at base, and others becoming smaller 
and more directed upward as the 
stem is ascended. 
