ESSENTIAL ORGANS. STAMENS. 



187 



flower of almond (fig. 308), in which the petals, p, and the stamens, e, 

 are united to the calyx, c, while the pistil is free. When the union 

 of the parts of the flower is such that the stamens are inserted upon 



307 308 



the ovary, they are epigynous (i^i, upon or above). In this case, the 



whorls are usually so incorporated, that the stamens appear also to 



come from the calyx. In Aralia spinosa (fig. 309), all the whorls, 



calyx, c, petals, p, and stamens, e, are united to the pistil, and the two 



latter whorls appear to arise from the point 



where the calyx joins the upper part of the 



pistil. These arrangements of parts have 



given rise to certain divisions in classification, 



to be afterwards particularly noticed. De- 



candolle, for instance, applies the term thala- 



miflorce, to plants having the parts of the 



corolla and androecium independent of each 



other, and all the whorls inserted immediately 



into the torus or thalamus ; calyciflorce, to those where the petals are 



separate, and the stamens are inserted directly on the calyx ; corolli- 



florce, to those in which the united petals bear the stamens. 



Fig. 306. Central part of the flower of Liriodendron tulipifera, the tulip-tree, composed of 

 carpels, c c, which together form the pistil. They cover the upper part of the axis, a, and below 

 them are inserted numerous stamens, some of which are seen, e e. These stamens are hypogy- 

 nous and extrorse. 



Fig. 307. Section of a flower of Geranium robertianum. c c, Calyx, p, Petals, e, Stamens. 

 Pistil composed of ovary, o, and style and stigmata, s. t, Torus or thalamus. The petals and 

 stamens are hypogynous, and the latter are monadelphous. 



Fig. 308. Section of the flower of the Almond-tree. The letters indicate the same parts as in 

 the last figure. The petals and stamens are perigynous. The pistil is free. 



Fig. 309. Section of the flower of Aralia spinosa. Letters as in last figure. The petals and 

 stamens are epigynous, attached to a large disk, rf, which covers the summit of the ovary. The 

 ovary is adherent to the calyx, and has been laid open to show its loculaments and pendulous 

 ovules. 



