22 



BUDS 



and have buds in their axils. Often it is an easy matter to 

 cause these axillary buds to develop into branches; for in- 

 stance, if we nip off the stem of a Scarlet Runner just above 

 the points of insertion of the cotyledons, the buds in the axils 

 of the latter will shoot out and become branches, (ii.) In 

 many plants transitions from foliage - leaves to bracts {e.g. 

 Rose, Christmas Rose), or to scales {e.g. buds of the Horse- 

 chestnuts), or even to cotyledons, occur, (iii.) It is possible 

 to cause foliage-leaves to appear in place of scales; for ex- 

 ample, some stems {e.g. Potato-tubers), which are normally 

 subterranean, when caused to develop above ground, pro- 

 duce foliage-leaves instead of small scales. 



BUDS. 



.ffistivation is the term applied to denote the arrangement 



of the different leaves of a bud with reference to one another. 



In the bud the leaves forming a single whorl or spiral may 



not be in contact, in which case the aestivation is said to be 



Figs. 29-37. — Diagrams of Vernation. In figs. 32-37 the shaded face Qf leaf is the 

 upper face. The leaves are transversely cut. 



Open. When their edges just touch, without overlapping, the 

 aestivation is valvate. Finally, when the leaves overlap the 

 aestivation is imbricate. 



