122 KINDS OF BULBS. 
(figs. 261-263), which are described by us as enlarged roots, are 
considered by some botanists as tubers. The tuber, however, 
as defined above, is well characterised, and, in practice at least, 
should be distinguished from them. 
ce. The Bulb.—This is a sh8rtened, usually subterranean 
stem or branch, generally in the form of a rounded or flattened 
plate or disc (figs. 239-241, a), which bears on its surface a 
number of fleshy scales or cataphyllary leaves ; or it may be 
considered as a subterranean bud of a scaly nature which sends 
off roots or rootlets from below (fig. 241, b), and a flowering 
stem upwards (fig. 239, p, and figs. 240 and 241, d). The scales 
are generally more or less thickened by deposition of nutritive 
matters ; these, therefore, serve as reservoirs of nutriment for 
the future use of the plant, just as in other cases the enlarged 
stems and roots serve a similar purpose. The true bulb is only 
Fig. 239. Fia. 240. Fic. 241. 
Fig. 239. Vertical section of the scaly bulb of the Lily. a. Shortened axis or 
stem. 0. Lateral bulb or clove. p. Flowering stem. c. Scales.—Fig. 
240. Vertical section of the scaly bulb of the Lily. Fig. 241. Scaly bulb 
of the Lily. a. Shortened axis or stem. }. Fibrous roots. ¢, Scales. d. 
Flowering stem, The letters refer to the same parts in the two latter 
figures, 
found in Monocotyledons, as in the Lily (figs. 240 and 241), 
Onion (fig. 242), and Tulip. The scales of a bulb, like the 
leaves of a branch, have the power of developing in their axils 
new bulbs (fig. 239, b); these are called by gardeners cloves, and 
their presence is an additional proof of the analogy of a bulb 
to a branch or bud. 
There are two kinds of bulbs commonly distinguished by 
botanists, namely, the twnicated (fig. 242), and the scaly (figs. 
240 and 241). The tunicated bulb is well seen in the Onion (jig. 
242) and Squill. In this kind of bulb the inner scales, which 
are thick and fleshy, enclose each other in a concentric manner, 
and are covered externally by thin and membranous ones, 
which form a covering or twnic to them, and hence the name 
timicated or coated, which is applied toit. In the scaly, or naked 
bulb, as it is also called (figs. 240 and 241), there are no outer 
