94 LEAF-BUDS AND BRANCHES. 



canal which is closed at both extremities, and which sends prolonga- 

 tions of spiral vessels to the leaves. As the axis or central portion of 

 the leaf-bud increases, cellular projections appear at regular intervals, 

 which are the rudimentary leaves. 



181. A leaf-bud may be removed in a young state from one plant 

 and grafted upon another, by the process of budding, so as to continue 

 to form its different parts; and it may even be made to grow in the soil, 

 in some instances, immediately after removal. In certain cases, leaf- 

 buds are naturally detached during the life of the parent, so as to 

 form independent plants, and thus propagate the individual. Leaf- 

 buds have on this account been called fixed embryos, by Petit-Thouars 

 and others. They are embryo plants fixed to the axis, capable of send- 

 ing stems and leaves in an upward direction, and woody fibres down- 

 wards, which, according to some, may be considered as roots. A tree 

 may be said to consist of a series of leaf-buds, orphytons (Qv-rov, a plant), 

 attached to a common axis or trunk. In ordinary trees, in which there 

 is provision made for the formation of numerous lateral leaf-buds, any 

 injury done to a few branches is easily repaired ; but in Palms, which 

 only form central leaf-buds, and have no provision for a lateral forma- 

 tion of them, an injury inflicted on the bud in the axis is more likely 

 to have a prejudicial effect on the future life of the plant. 



182. In the trees of temperate and cold climates, the buds which 

 are developed during one season lie dormant during the whiter, ready 

 to burst out under the genial warmth of spring. They are generally 

 protected by external modified leaves in the form of scales, tegmenta or 

 perulce (tegmenta, coverings, peruke, small bags), which are of a firmer 

 and coarser texture than the leaves themselves. These scales or pro- 

 tective appendages of the bud, consist either of the altered lamina, or 

 of the enlarged petiolary sheath, or of stipules, as in the Fig and Mag- 

 nolia, or of one or two of these parts combined. They serve a tempo- 

 rary purpose, and usually fall off sooner or later after the leaves are 

 expanded. The bud is often protected by a coating of resinous mat- 

 ter, as in the Horse-chestnut and Balsam poplar, or by 

 a thick downy covering, as in the Willow. Linnajus 

 called leaf-buds hibernacula, or the winter quarters of the 

 young branch. 



183. In the bud of a common tree, as the Syca- 

 more (fig. 203), 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 

 203 is called an imbricated (imbrex, a roof tile) manner. 



nr^w a i^'J"^ f "^ ud of ^ c ^ r Pscudo-platanus covered with scales, r, The branch, p, Pulvinus 

 or swelling at the base of the leaf which has fallen, leaving a scar or cicatricula, c, in which the 

 remams of three vascular bundles are seen, e, e, Imbricated scales of the bud. 



