98 



OHGANOGRAPHY. 



Fig. 187. 



Fig. 188. 



Fig. 189. 



Fig. 187. Leaf of Bryophyllum calycinum with buds on its margin. Fig. 



188. End of the leaf of Malaxis pahidosa, with buds, b, b, on its mar- 

 gin. Fig. 189. A portion of the leaf of Ornithogalum thyrsoideum, 



showing buds, b, b, b, on its surface. 



Embryo-Buds. — In some trees the adrentitions buds, instead 

 of being developed on the outside of the stem, are enclosed in the 



bark. Such have been 

 called embryo -buds op 



Fig. 190 



nodules. They may be 

 readily observed in the 

 bark of certain trees, 

 such as the Cork-oak, 

 the Beech, and the 

 Cedar of Lebanon, 

 in which they produce 

 externally little swel- 

 lings, which, when exa- 

 mined, are found to be 

 owing to the presence 

 of these nodules, which have a more or less irregular ovoid or 

 spheroidal form {fig. 190), and woody texture. Upon making 

 a transverse section of one of them {fig. 191), we observe 

 a central pith surrounded by concentric zones of wood (the 

 number of which varies according to its age as in ordinary 

 trees), and traversed by medullary rays ; in fact, it has all 

 the elements of organization found in the trunk of a tree. In 

 the course of their development these embryo-buds frequently 

 reach the wood, with the growth of which they become con- 

 founded- and thus form what are called knobs. In other cases 



Fig. 190. Embryo-bud or nodule of the Cedar. 



Fig. 191. A vertical section of the same 



surrounded by the bark. 



