ORGANS OF NUTRITION. 



105 



more or less in-egular ovoid or spheroidal form {fig. 198), 

 and woody texture. Upon making a transverse section of one of 

 them {fig. 199) 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, as 

 stated by Dutrochet, it has all the elements of organization found 

 in the trunk of a tree. In the course of their development these 

 embr}'0-buds frequently reach the wood, with the growth of 

 which they become confounded and thus form what are called 

 knobs. In other cases a number of nodules meeting together 

 on the surface form an excrescence. That such nodules are 

 analogous to buds is proved by the fact of their sometimes 

 producing a short branch from their summits, as in the Cedar of 

 Lebanon and in the Olive. Those of the latter plant, under 

 the name of Uovili, are really employed for its propagation. 

 Lindley also states that he has a number of these nodules which 

 he received from Prince of Wales' Island, which exhibit all 

 sorts of transitions, from their common irregular spheroidal form 

 to modified branches. Hence there can be no doubt of their 

 analogy to buds. The peculiar appearance of the wood of the 

 Bird's-eye Maple is said to be caused by the presence in it of 

 these nodules. 



3. Accessory Buds. — The third cause of irregularity in the dis- 

 tribution of branches arises from the multiplication of buds in 



Fiu. 200. 



Fig. 202. 



Fig. 200. Branch of a species of Maple with three buds, a, 



placed by the side of one another Fig. 201. A piece of 



the branch of the Walnut-tree. p. The petiole having 

 in its axil a number of buds, b, placed one above the other, 



the uppermost most developed. Fig. 202. A piece of the 



branch of the Tartarian Honeysuckle (Loniiiera tartarica), 

 bearing a leaf with numerous buds in its axil placed above 

 one another, the lowermost being the most developed. 



the axils of leaves. Thus, instead of one bud, we have in rare 

 cases two, three, or more thus situated, such are called accessory 



