TREES AND SHRUBS. 



397 



scales and occasionally two small leaves, and ending in a 

 loose drooping catkin. The catkin- scales are large and con- 

 cave; each bears from four to twelve stamens, and each 

 stamen has a forked filament with a half -anther on each fork. 

 The female catkins, which usually stand higher up the twig, 

 develop from a bud which produces at its base foliage-leaves 

 as well as scales. They are narrower than the male catkins, 

 and in the axil of each catkin- scale there are two female 

 flowers resembling those of Hazel ; at the base of each flower 

 there is a small three-lobed scale. 



The fruits (Fig. 163) are ribbed nuts, each showing at the 

 top the five lobes of the perianth, while the small scale 

 around the flower grows into a large three-lobed structure 

 (corresponding to the cupule of Hazel) which clasps the 

 fruit below and acts as a wing, helping in wind- dispersal ; 

 the narrow catkin-scales fall off after pollination. 



I. Oak (Quercus robur), the largest of British trees, 

 sometimes 150 feet high, with 

 massive trunk, is easily recognised 

 at all times of year. Even when 

 without its wavy-lobed leaves or 

 its acorns, it differs from other 

 trees in its gnarled and contorted 

 main branches and in having its 

 buds crowded round the ends of 

 the twigs (see Art. 179). 



In the commoner variety of the 

 Common Oak (Stalked Oak) each 

 group of acorns is carried on a 

 stalk ; in the other variety (Ses- 

 sile Oak) the acorn-group has no 

 stalk. The Oak leaf has small 

 stipules which soon fall off. In 

 Stalked Oak there is no leaf-stalk 

 or a very short one, in Sessile Oak 

 the leaf-stalk is long; in Sessile 

 Oak the blade is firmer, more tapering at the base, and has 

 hairs on its lower side. 



The flowers appear with the leaves in April or May. The 

 male catkin bears numerous flowers scattered singly or in 



Fig. 165. The Stalked Oak, with 

 Flowers. 



