no 



VERNATION OR PEiEFOLIATION. 



They serve a temporary purpose, and usually fall off sooner or later 

 after the leaves are expanded. The bud is often protected by a coat- 

 ing of resinous matter, as in the Horse-chestnut and Balsam poplar, or 

 by a thick downy covering, as in the Willow. Linnseus called leaf- 

 buds hibernacula, or the winter quarters of the young branch. 



In the bud of a common tree, as the Sycamore (fig. 220), there is 

 seen the cicatrix left by the leaf of the previous year, c, with the 

 pulvinus or swelling, p, then the scales, e e, arranged alternately in a 



spiral manner, and 

 overlying each other 

 in what is called an 

 imbricated (imbrex, a 

 roof tile) manner. On 

 making a transverse 

 section of the bud (fig. 

 221), the overlying 

 scales, e e e e, are dis- 

 tinctly seen surround- 

 ing the leaves,/, which 

 are plaited or folded 

 round the axis orgrow- 



Fig 220. Fig. 221. . ■ J. T 1 i. 



^ mg point. In plants 



of warm climates the- buds are often formed by the ordinary leaves 

 without any protecting appendages ; such leaves are called naked, 



Veenation. — The arrangement of the leaves in the bud has been 

 denominated vernation (ver, spring), or proefoliation (jprx, before, and 

 folium, leaf), or gemmation {gemma, a bud). In considering vernation 

 we must take into account both the manner in which each individual 

 leaf is folded and also the arrangement of the leaves in relation to 

 each other. These vary in different plants, but in each species they 

 follow a regular law. The leaves in the bud are either placed simply 

 in apposition, as in the Mistleto, or they are folded or rolled up 

 longitudinally or laterally, giving rise to different kinds of vernation, 

 as delineated in fig. 222 o-n, where the dot represents the axis and 

 the folded or curved lines represent the leaves, the thickened part in- 

 dicating the midrib ; figs, a and g being vertical sections ; l-f and 

 h-n, horizontal. 



The leaf taken individually is either folded longitudinally from 

 apex to base (fig. 222 a), as in the Tulip-tree, and called reclinate 

 or replicate ; or rolled up in a circular manner from apex to base, as 



Fig. 210. Leaf-ljud of Sycamore {A(xr 'pseudo-^laiawm} covered with scales. /, The 

 branch. ;p, Pulvinus or swelling at the base of the leaf which has fallen, leaving a scar or 

 cicatricula, c, in which the remains of three vascular bundles are seen, e e, Imbricated scales 

 of the bud. Fig. 221, Transverse section of the same leaf-bud. e e e e. The scales arranged 

 in an imbricated manner, like the tiles on a bouse. /, The leaves folded in a plaited manner, 

 exhibiting plicate vernation. 



