306 STRUCTURAL BOTANY 



the ovary, so that fertilisation has to take place through 

 the mediation of the stigma and style. The remarkable 

 development of the floral leaves, characteristic of most 

 Angiosperins, is connected with the occurrence of polli- 

 nation by insects, for which so many Angiosperins are 

 specially adapted. 



At present we are not in a position to determine 

 either the relation of Angiosperins to Gymnosperms, 

 nor that of Monocotyledons to Dicotyledons. The latter 

 classes are mainly distinguished by vegetative char- 

 acters, the reproductive phenomena being the same in 

 both. On both these questions, however, we may hope 

 for further light, especially from palceontological research, 

 for the first appearance of Angiosperms falls within a 

 geological period from which abundant fossil remains 

 have come down to us. Dr. Wieland's discovery that 

 the Bennettitese, Mesozoic plants allied to Cycads, 

 produced elaborate hermaphrodite flowers, comparable 

 to those of the Angiosperms, has already thrown an 

 entirely new light on these questions. 



This brief summary has had one main object, to 

 indicate the complicated and difficult nature of all ques- 

 tions as to the affinities of plants. Naturalists in these 

 days are agreed that the different forms of plants and 

 animals arose from one another by descent. If this be 

 so, a natural classification of the vegetable kingdom 

 would take the form of a genealogical tree, just like the 

 pedigree of a family. The genealogical tree of plants 

 must have been complex beyond all power of conception, 

 with boughs, branches, and twigs of every degree starting 

 from each other at every possible point, some long and 

 some short, a few reaching on to our own day, while the 



