Trees; a handbook of forest-botany for the woodlands and the laboratory . —e Fig. 12. Pinnate, compound leaf of Dog Rose, llosa eanina. a lateraland <l terminal leaflet; b rachis; c adnate stipules, e midrib ; / second-ary and (j tertiary veins of leaflet; h petiolule (Ett). 42 PALMATE LEAF [CH. stalk attaching it to the latter, such stalk is termed Fig. 13. Palmate, compound leaf of Horse-chestnut, MsculusHippocastanum, with five leaflets (D). A conspicuous feature at the base of most compoundleaves, and of many simple ones also, especially largeleaves, is a cushion-like round
Trees; a handbook of forest-botany for the woodlands and the laboratory . —e Fig. 12. Pinnate, compound leaf of Dog Rose, llosa eanina. a lateraland <l terminal leaflet; b rachis; c adnate stipules, e midrib ; / second-ary and (j tertiary veins of leaflet; h petiolule (Ett). 42 PALMATE LEAF [CH. stalk attaching it to the latter, such stalk is termed Fig. 13. Palmate, compound leaf of Horse-chestnut, MsculusHippocastanum, with five leaflets (D). A conspicuous feature at the base of most compoundleaves, and of many simple ones also, especially largeleaves, is a cushion-like rounded swelling, the so-calledpulvinus, particularly prominent on the lower side wherethe petiole abuts on the shoot-axis. This pulvinus is IV] PULVINUS. LEAFLETS 43 known to be a motile organ, and consists of soft cellulartissue capable of taking up water into its cells, somewhatas a pump takes it up though the action is different indetail. When it becomes surcharged with water thepulvinus expands, especially beneath, and forces thepetiole into a more erect position ; when the pulvinuspartially empties itself, the weight of the leaf compressesit, and the petiole falls, and considerable differences ofangular divergence in the vertical plane may be under-gone by the rigid petiole or rachis turning on its insertionas on a fulcrum. Each leaflet may also have its o
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Keywords: ., bookcentury1900, bookdecade1900, bookidtreeshandboo, bookyear1904
