CHAPTER XXX. 



DICOTYLEDONS. 



IN this group of plants the embryo has two cotyledons, the 

 leaves are netted-veined, and the plants grow in diameter by the 

 addition of new material each year between the bark and wood 

 of the previous year, as among the gymnosperms. This sub- 

 class contains nearly 200 natural orders or families, but only a 

 few of the more interesting and valuable can be noticed here. 



The Willow Family consists of trees or shrubs, with bitter bark, 

 light, soft wood, and dioecious flowers that is, the male and fe- 

 male organs are in separate flowers on separate plants. Both 

 kinds of flowers are in clusters called catkins, which are much like 

 cones, only the scales are more leaf-like and the axis more slender. 

 The staminate or sterile flower consists of stamens only, the 

 pistilate or fertile flower of one pistil with a one-celled ovary. At 

 maturity the ovary contains numerous seeds each of which is fur- 

 nished with a tuft of cotton-like down at one end. This family 

 includes the willows, osiers, aspens, poplars, and the cotton- 

 wood. Some of these trees are grown for ornament; from the 

 aspen, pulp for coarse paper is made, and willow-ware is made 

 from the young shoots of the osier. 



The Oak Family consists mainly of trees, with some shrubs, 

 bearing alternate leaves, which are sometimes entire and some- 

 times pinnately lobed or cleft. The flowers are monecious or di- 

 clinous, both on the same plant; the sterile in slender catkins, 

 the fertile, solitary or clustered. Among the oaks proper, the 

 sterile flowers have a four to seven lobed calyx, and from three to 

 twelve stamens clustered in pendant catkins, while the fertile 

 flower is one pistil in a bud-like involucre that becomes a scaly 

 cup, called the cupule, which partly covers the brown ovoid nut 

 or acorn. 



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