82 VEGETABLE ORGANOGRAPHY. 



sure and etiolation as powerful as that which in the 

 Dipsaceae results from the vicinity of other flowers. The 

 genera where the limb is not rolled inwards have it 

 developed into foliaceous teeth, as in ordinary calyces. 



The abortion or complete absence of the sexual 

 organs of plants, or of one of them, is a phenomenon 

 which constantly happens in all plants said to be Uni- 

 sexual, and accidentally in several others. Thus, to 

 commence with the latter case, which is the clearer, 

 Lychnis dioica, although belonging to a family usually 

 hermaphrodite, presents certain individuals where the 

 female organs are well-developed, and then the stamens 

 are reduced to simple rudiments ; and others where the 

 stamens are well developed, and where the pistil is 

 abortive, so that in its place is only seen a little pro- 

 tuberance with the rudiments of five stigmata. The 

 same phenomenon takes place in Spircea Aruncus and 

 Sedum Rhodiola, Sec. All plants which present this 

 phenomenon accidentally are said to be Dioecious by 

 abortion ; thus, in several Compositae, part of the 

 flowers of each head are devoid of ovary, style, and 

 stigma by abortion, and others have no perfect stamens, 

 so that they are Moncecious by abortion. Thus, in 

 Diospyrus, Gleditsia, &c, a part of the flowers are 

 devoid of pistils, another of stamens; and we find, 

 besides, others where the two organs exist together, 

 constituting that state of flowers which botanists have 

 called Polygamous by abortion. 



These three systems of flowers, unisexual by abortion, 

 are frequently met with in almost all the families where 

 we also find hermaphrodite ones ; such are the Caryo- 

 phyllea?, Compositae, Valerianese, Ebenaceae, Thyme- 

 laeae, Leguminosae, &c. ; and in all these cases it is 

 evident that the two sexes exist typically, and that one 

 of them is not developed. 





