36 THE VEGETATIVE FUNCTIONS OF PLANTS 
converge at the base of the blade (Fig. 22). They may be 
traced from this point, through the petiole, into the 
branch. The veins are composed of fibers and vessels, 
FIG. 28. Horse-chestnut (Aesculus Hippocastanuni). Is, leaf-scar, 
showing scars of seven nbro-vascular bundles, corresponding, in number, 
to the seven leaflets of the compound leaf, formerly attached at Is. The 
leaf is drawn to a smaller scale than the branch. 
closely associated, and are, therefore, called fibro-vascular 
bundles. A cross-section of the petiole of a horse-chestnut 
leaf, for example, shows one fibro-vascular bundle for 
each leaflet of the compound blade (Fig. 28) ; each of the 
