210 



WHITE POPLAR, ETC. 



Petioles of smaller leaves 2 3 cm. long, round and slender, 

 those of larger leaves 5 9 cm. and compressed, white- 

 tomentose. Lamina thick and tough, deep green and be- 

 coming glabrous above (the venation paler), densely white 

 cottony or tomentose beneath ; though there are varieties 

 where this tomentum is greyer or even disappears. Upper 

 stomata absent. Autumn leaves dark brown. 



Venation as in P. alba, var. canescens, but more palmate, 

 in accordance with the greater segmentation of the leaf. 



[The leaves of Pyrus Aria are sometimes pinnately 

 lobed, or even completely pinnate below (p. 175), and the 

 more pubescent forms of Quercus Robur, var. pubescens, may 

 be hoary white beneath (p. 215).] 



tt Leaves not tomentose beneath, but glabrous 

 or nearly so ; cuneiform, with more or less 

 tapering base. The alternate secondaries 

 fork over the sinuses. Shoots thorny. 



Gratwgus Oxycantka, L. Hawthorn, Whitethorn (Fig. 

 66). Thorny shrub. Leaves variable, 3 7 x 2 6 cm., 



Fig. 66. Hawthorn, Crateegus Oxycantha, p. 210 (D). 



broadly ovate or obovate, cuneiform, entire at the base, cut 

 sometimes very deeply into 35, or even 7, pseudo-palmate 



