116 ANOMALIES AND TRANSFORMATIONS OF LEAF-BUDS. 



the head of subterranean stems (p. 48, fig. 110). It may be considered 

 as a bulb in which the central portion or axis is much enlarged, whUe 

 the scales are reduced to thin membranes. Some have called it a 

 solid bulb. A Oorm may be generally distinguished from a Bulb by 

 a transverse section of the latter presenting a series of circles, equal in 

 number to the fleshy scales arranged around its central axis. It is 

 seen in the Colchicum, Crocus, and Gladiolus. It produces either 

 terminal buds, as in Gladiolus and Crocus, in which several annual 

 additions to the corm remain attached together, and the newly pro- 

 duced corms come gradually nearer and nearer to the surface of the 

 soil ; or lateral buds, as in Colchicum, represented at fig. 110, where r 

 indicates the roots, / the leaf, a' the stem or axis of the preceding 

 year withered, a" the secondary axis, or the stem developed during 

 the year, and taking the place of the old one, and which, in its turn, 

 will give origin to a new axis, a'", on the opposite side, according to 

 the law of alternation. The new axes or corms being thus produced 

 alternately at either side, there is very little change in the actual 

 position of the plant from year to year. Bulbs and corms contain a 

 store of starch and of other substances, for the nourishment of the 

 young plants. 



Anomalies and Teansformations of Leaf-Buds. — Leaf-buds 

 arise from the medullary system of the plant, 

 and in some instances they are found among 

 the cellular tissue, without being in the axU of 

 leaves. In this case they are extra-axillary, 

 and have been called adventitious or abnormal. 

 Such buds are produced after the stem and 

 leaves have been formed, and in particular 

 circumstances they are developed like normal 

 J,. 2^. buds. What have been called embryo-buds are 



woody nodules seen in the bark of the Beech, 

 Elm, and other trees. They are looked upon as partially developed 

 abnormal buds, in which the woody matter is pressed upon by the 

 surrouading tissue, and thus acquires a very hard and firm texture. 

 When a section is made, they present woody circles arranged around 

 a central pith, and traversed by medullary rays (fig. 227). The 

 nodules sometimes form hnots on the surface of the stem, at other 

 times they appear as large excrescences, and in some cases twigs and 

 leaves are produced by them. Some consider embryo-buds as formed 

 by layers of woody matter, which originate in the sap conveyed 

 downward by the bark and cambium cells, and are deposited round 

 a nucleus or central mass. 



Pig. 227. Vertical section of a nodule, n, or embryo-lmd embedded in the bark of the 

 Cedar. It forms a projection on the surface. The woody layers form zones round a kind of 

 pith. 



