240 



TIIK PLOTTER. 



even in the same natural family of plants, where it cannot be doubt- 

 ed that the blossoms are constructed upon a common plan in all the 

 species. Even in the family Crassulacea>, for example, where the 

 flowers are remarkably symmetrical, and from 

 which our pattern flowers, Fig. 334 and 353, 

 are derived, a considerable number of these di- 

 versities are to be met with. In Crassula, Ave 

 have the completely symmetrical and simple 

 pentamerous flower (Fig. 359, 3C0), viz. with a 

 calyx of five sepals, a corolla of five petals alter- 

 nate with the former, an andrcccium (418) of 

 five stamens alternating with the petals, and a 

 gynaecium (419) of five pistils, which are alter- 

 nate with the stamens ; and all the parts are 

 regular and symmetrical, and also distinct and 

 free from each other ; except that the sepals are 

 somewhat united at the base, and the petals and 

 330 stamens slightly connected with the inside of the 



calyx, instead of arising directly from the recep- 

 tacle or axis, just beneath the pistils. Five is the prevailing or 

 normal number in this family. Nevertheless, in the related genus 

 Tillrea, most of the species, like ours of the United States, have 

 their parts in fours, but are otherwise similar, and one common 

 European species has its parts in threes (Fig. 353) ; that is, one or 

 two members are left out of each circle, which of course does not in- 

 terfere with the symmetry of the blossom. So in the more conspic- 

 uous genus Sedum (the Stoneerop, Live-for-ever, Orpine, &c), some 

 species have their parts in fives ; others 

 in fours ; and several, like our S. ter- 

 natum, have those of the first blossom 

 in fives, but all the rest in fours. But 

 Sedum also illustrates the case of reg- 

 ular augmentation (447, 1st) in its an- 

 droccium, which consists of twice as 

 many stamens as there are members 

 in the other parts ; that is, an addi- 

 tional circle of stamens is introduced (Fig. 3C>1), the members of 

 which may be distinguished by being shorter or a little later than 



FIG 359 Flower of a Crassula. 3H0 Cross-section of the bud. 

 FJG. 361 Flower of a Seduui or Stoneerop. 



