The wild rose.—The plants of the rose family are, most commonly, woody trees or shrubs. The leaves are provided with stipules in nearly all cases. The wild rose ([Fig. 75]) may be taken as a type of the group. It bears a superficial resemblance to a buttercup, but on dissection considerable difference in the arrangement of the parts is seen. In the rose, the receptacle is urn-shaped; from the margin of the urn spring the five sepals, five petals, and numerous stamens; while inside the urn the separate carpels of the pistil are inserted. In the blackberry ([Fig. 76]), raspberry, and strawberry the receptacle is knob-shaped, and the carpels are arranged on the outside of the knob, somewhat as in the buttercup. Here again, however, the calyx, corolla, and stamens differ from those of the buttercup in seeming to arise from a common base.
Fig. 76.—Blackberry. 1, flowering branch (× ⅓);
2, longitudinal section of flower (× 1);
3, fruit (× ⅓); 4, diagram of flower.
Fig. 77.—Cherry. 1, flowering branch (× ⅔);
2, longitudinal section of flower;
3, longitudinal section of fruit.
The differences between the rose, blackberry, raspberry, and strawberry are more marked when the pistil has become a fruit. The fleshy part of the rose hip is the urn-shaped receptacle which encloses the ripened carpels. In the case of the blackberry and raspberry the receptacle is dry, and is surrounded by the compound fruit ([Fig. 76], 3) of the several bodies like little plums or cherries. The eatable part of the strawberry fruit ([Fig. 144]) is the swollen receptacle, on the outside of which are the little yellow nutlets derived from the carpels of the flower.
In the cherry ([Fig. 77]), plum, and apricot the pistil consists of only one carpel, which is enclosed in the urn-like receptacle. After fertilisation, the greater part of the wall of the ovary becomes fleshy, and one of the two ovules contained in it becomes a seed. The “stone” is formed from the innermost part of the ovary wall.