TUBER. 



73 



178. The BULB(partakes of the natm-e of the bud. It consists 

 of an oval mass of short, tMckened scales, closely compacted in 

 concentric cn-cles and layers, emitting a stem from their- midst 

 and roots from the base or coUum) {14,1). ' 



a. Bulbs are said to be timicated when they consist of concentric layers each 

 entu-e, and enclosing all within it, as in the Onion. But the more common 

 variety is the scaly bulb, consisting of tliickened concave scales, connected to- 

 gether at the base, as the lily, tulip. 



b. The bulb is renewed annually, at tlie approach of winter, by the develop- 

 ment of new bulbs in the axils of the scales, which increase at the expense of the 

 old.^ 



c. Btdblets^e small, aerial bulbs, formed in the axils of the leaves upon the 

 stem, wUch, when matured, fall to the ground, take root, and produce a perfect 

 plant. The tiger-lUy (Lihum bulbiferum) is an example, also several species of 

 the onion. Such plants are tenned bnlbiferous. 



FIG. 2.5. -Forms of the stem ;- 1, Allium ; 2, Arum; 3, Solanum tuberosum; ^ San- 

 guuiana ; 5, a spinous branch. ' 



179. The coRM.is the dilated, subterranean base of a stem, 

 resembling the bulb in form and position, but differing in struc- 

 ture, being composed of a uniform and solid mass, without dis- 

 tinction of layers or scales. It has been improperly caUed a 

 solid hulh. Ex. Ai-um, or Lidian turnip'.) 



ISO. The TUBER, is an annual, thickened portion of a subter- 

 ranean stem, provided Avith latent buds (called eyes), from 

 Avhich nevvT plants arise the succeeding year. It is the develop- 

 ment of buds, and the fact of its origin with the ascending eocis, 

 tliat places the tuber among stems instead of roots. The pota- 

 toe is an example. 



