. Plant studies; an elementary botany. Botany. 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. I
. Plant studies; an elementary botany. Botany. 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 Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Coulter, John Merle, 1851-1928. New York, D. Appleton and Company
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