XV] SHAPES OF LEAF-SCARS 117 



In most of the other species to be dealt with the leaf- 

 scars are of medium size. 



Their shapes differ exceedingly, and are best under- 

 stood with reference to Fig. 59. 



The leaf-scars are nearly circular in the Fig (Fig. 59 a) ; 

 shield-shaped or heart-shaped in the Horse-chestnut and 

 Ailanthus glandulosa (Fig. 59 b and c) ; more or less 

 Y-shaped, U-shaped, or V-shaped in the Walnut, the 

 Vine, Ampelopsis hederacea, and Maples (Fig. 59 c?, e,f}\ 

 crescentic in the Sycamore, Apple, some Oaks, Roses and 

 Blackberry, Red and Black Currants, Rowan, Wayfaring 

 Tree, Guelder Rose, Dogwood, Pear, Beam, and Willows 

 (Fig. 59 g, h) ; almost ring-shaped in Rhus typhina and 

 the Plane (Fig. 59 i } k) ; approximately half-moon-shaped 

 in the Aspen, Turkey Oak, Red Oak, Black Poplar, White 

 Poplar, Lime, Barberry, Laburnum, &c. (Fig. 59 I, m, o); 

 more or less kidney-shaped in some Oaks, Plum, Sweet 

 Gale, Honeysuckles, Buckthorn, Genista tinctoria, Cherries, 

 &c. (Fig. 59 n, jt)); nearly elliptical in Beech, Hornbeam, 

 the Bird Cherry, Privet, Daphne, the Sea Buckthorn, Elms, 

 Symphoricarpos, Broom, &c. (Fig. 59 g, r, s) ; and nearly a 

 straight linear scar in the Birch (Fig. 59 v). 



Since the vascular bundles forming the venation of the 

 leaf pass down the petiole or leaf-stalk into the twig, 

 there to join the vascular strands of the stem, it follows 

 that when the leaf falls these bundles are cut across at 

 the plane of the separation-layer, and their transverse 

 sections are left on the leaf-scar. In the case of the larger 

 leaf-scars these cut ends of the leaf-traces the term 

 applied to the groups of vascular strands passing from 

 leaf to twig are very evident ; for instance they represent 

 the " nails " in the " horse-shoe " of the " hoof " which the 

 leaf-scars of the Horse-chestnut or of Ailanthus (Fig. 59 

 6 and c) may be said to represent. 



