328 APPENDIX II 



a merely protective structure. In so doing, it must give up the 

 idea of insect-pollination in favour of self-pollination or wind- 

 pollination. 



These distinctions are made use of in classification. The 

 Dicotyledons fall into three classes, known as the Pdlypdalce, 

 GamopetaloE and Apetalae, according to whether their petals are 

 free, united, or absent. Within each of these groups we find 

 another tendency operating — namely, to proceed from a 

 hypogynous form of flower to a perigynous, and eventually to 

 an epigynous type. 



We may illustrate some of the chief varieties of floral 



Fig. XXVI. 



1, The Flower of a Buttercup (natural order Ranunculaceae). 



2. Petal of a Buttercup, showing the Honey-gland at the base. 



structure by reference to five flowers, of which text-figures are 

 given here. Each diagram represents the flower cut in half 

 longitudinally. The Buttercup (Text-fig. XXVI.) is a 

 hypogynous flower, polysepalous and polypetahus. Both the 

 stamens and carpels are numerous, and free from one another. 

 Each carpel contains a single seed. The Buttercup is called a 

 regular flower, because all the parts of each whorl are alike in 

 shape and size. 



The next text-figure (XXVII.) represents a Pea flower, in 

 which the five petals differ amongst themselves in size and 



