52 ELEMKNTS OP STRUCTURAL BOTANY. 



called, the fact that the flowers are not to be obtained 

 without effort on account of their distance from the ground, 

 as well as the circumstance of their being rather incon- 

 spicuous, may lead to their being overlooked unless special 

 attention is directed to them. The White Oak is perhaps 

 the best known species with us. It may be pretty well 

 distinguished from other species by its leaves, the lobes of 

 which (Fig. 65) are rounded. However, for the purposes 

 of this lesson, any other species may be used, if the White 

 Oak is not at hand. The flowers are monoecious, the 

 sterile ones forming long and slender drooping catkins, 

 which are either single or, more generally, several in a 

 cluster, from the same lateral bud (Fig. 66). Each sterile 

 flower (Fig. 67) consists of a perianth or calyx of a vari- 

 able number of sepals, mostly from four to six, and gen- 

 erally eight stamens. The fertile flowers spring mostly 

 from the axils of the leaves of new shoots, and they occur 

 either singly or two or three in a cluster. Each flower 

 consists of a syricarpous pistil of three carpels. The ovary 

 is three-celled, or nearly so, and two ovules are formed 

 in each cell. The flower is surrounded at the base by a 

 scaly involucre, which, at maturity, has become quite 

 woody, and forms in fact the cup in which the acorn rests. 

 If you dissect an acorn you will observe that there is but 

 one seed in it. Although the ovary contains six ovules at 

 starting, it always happens that all but one disappear 

 before the fruit is matured. 



The White Oak ripens its acorns the first year. The 

 Red Oak, on the other hand, does not ripen its fruit till 

 the autumn of the second year. 



72. It will be a valuable exercise to compare flowers of 

 the Beech with those just described. They will be found 



