SECTION 6.] 



STEMS. 



47 



116. Bulblets are very small bulbs growing out of larger ones ; or 

 small bulbs produced above ground oil some plants, as in the axils of the 

 leaves of the bulbiferous Lilies of the gardens (Fig. 110), and often iu the 

 flower-clusters of the Leek and Onion. They are plainly 



buds with thickened scales. They never grow into 

 branches, but detach themselves when full grown, fall to 

 the ground, and take root there to form new plants. 



117. Consolidated Vegetation. An ordinary herb, 

 shrub, or tree is evidently constructed on the plan 

 developing an extensive surface. In fleshy rootstocks, 



tubers, corms, and bulbs, the more enduring portion of the plant is con- 

 centrated, and reduced for the time of struggle (as against drought, heat, 

 or cold) to a small amount of 

 exposed surface, and this mostly 

 sheltered in the soil. There are 

 many similar consolidated forms 

 which are not subterranean. 

 Thus plants like the Houseleek 

 (Fig. 91) imitate a bulb. Among 

 Cactuses the columnar species of 

 Cereus (Fig. Ill, 6), may be lik- 

 ened to rootstocks. A green rind serves the purpose of foliage ; but the 

 surface is as nothing compared with an ordinary leafy plant of the same 

 bulk. Compare, for instance, the largest Cactus known, the Giant Cereus 

 of the Gila River (Fig. Ill, in the background), which rises to the height 

 of fifty or sixty feet, with a common leafy tree of the same height, such 

 as that in Fig. 89, and estimate how vastly greater, even without the foli- 

 age, the surface of the latter is than that of the former. Compare, in the 



FIG. 107. Bulb of a wild Lily. 108. The same divided lengthwise, showing two 

 forming buds of the next generation. 



FIG. 109. A ground leaf of White Lily, its base (cut acrossj thickened into 9- 

 tmlb-scale. This plainly shows that bulb-scales are leaves. 



FIG. 110. Bulblets in the axils of leaves of a Tiger Lily. 



