110 



THE STEM. 



kind of bulb with the axis more enlarged, and the investing scales 

 either wholly wanting, as in the Indian Turnip (Fig. 144), or very 

 few, forming a thin coating, as in the Colchicum and Crocus. 



177. A Bulb is a permanently abbreviated stem, mostly shorter 

 than broad, and clothed with scales, which are imperfect and altered 

 leaves, or the thickened and persistent bases of ordinary leaves. 

 Or, in other words, it is a scaly and usually subterranean bud, with 

 thickened scales, and a depressed axis which never elongates. Its 

 centre or apex developes above the herbaceous stalk, foliage, and 

 flowers of the season, and beneath it emits roots. In the bulb, the 

 thickening by the deposition of nutritive matter stored for future 

 use takes place in the leaves or scales it bears, instead of the stem 

 itself, as in the preceding forms. The scales are sometimes sepa- 

 rate, thick, and in several distinct rows, as in the scaly bulb of the 

 Lily (Fig. 141); sometimes broad and encircling each other in 

 concentric layers, as in the tunicated bulb of the Onion (Fig. 145). 



178. Bulblets are small aerial bulbs, or buds with fleshy scales, 

 which arise in the axils of the leaves of several plants, such as the 

 common Lilium bulbiferum of the gardens (Fig. 143), and at 

 length separate spontaneously, falling to the ground, where they 

 strike root, and grow as independent plants. In the Onion, and 

 other species of Allium, many of the flower-buds frequently change 

 to bulblets. They plainly show the identity of bulbs with buds. 



FIG. 141. The scaly bulb of a Lily. 142. A vertical section of the same, forming the an- 

 nual stalk. 143. Axillary bulblets of Lilium bulbiferum. 144, Corm of Arum triphyllum. 



