APPENDIX A 521 



Pollination. The flowers are conspicuous by their white petals, and honey 

 is secreted on the receptacular cup between stamens and carpels. They are 

 slightly protogynous. The result of repeated insect visits will thus be a 

 probability of cross-poUination, though self-pollination is also possible. 



(28) The flower of the Dog Rose {Rosa canina, L.) is constructed on a 

 plan similar to that of the Strawberry, but without the epicalyx. The chief 

 difference is in the receptacle, which instead of being convex with the carpels 

 carried up on the hemispherical axis, is hollowed into a sunken cavity. This 

 encloses the numerous bristly carpels, while their stigmas project above. 

 When mature the receptacle becomes succulent as in the Strawberry, forming 

 the " hip," with the nutlets or true fruits within. 



(29) The Cherry {Prunus cerasus, L.) has a construction of the flower 

 like that of the Rose, but with only one carpel borne in the hollow, cup-like 

 receptacle (Fig. 428). It consists of : 



Calyx, sepals 5, inserted upon the margin of the cup-like receptacle. The 

 odd sepal is posterior. 



Fig. 429. Fig. 430. 



Drupe of Cherry. (After Grouped drupels of the Raspberry. 



Figuier.) (After Figuier.) 



Corolla, petals 5, polypetalous, alternating with the sepals, 



Androecium, stamens indefinite, free, perigynous, i.e. inserted on the margin 

 of the receptacular cup. 



Gynoecium, carpel i, superior. The swollen ovary contains two ovules. 



Fruit, a drupe. The receptacular cup here dries up, and falls away. The 

 wall of the ovary differentiates into a superficial skin, a middle region of succu- 

 lent pulp, and an inner stony layer. The stone of the mature cherry contains 

 as a rule only one kernel, which is the exalbuminous seed, developed from one 

 of the ovules. Sometimes, however, both are matured. The Drupe thus 

 constructed is the type of fruit of Plums, Apricots, Peaches, etc. (Fig. jjti)- 



Pollination. The Cherry flower is not highly specialised. Anthers and 

 stigmas ripen simultaneously. Honey is secreted on the hollow surface of 

 1 he cup. It is visited by various short-lipped insects. 



The variability of Rosaceous flowers is illustrated by such examples. .\ 

 striking feature is the diversity of origin of the succulent pulp, which gives 

 \ alue to their fruits. In the Strawberry it arises from the convex receptacle ; 

 m the Rose from the concave receptacle ; in the Apple and Pear partly from 

 the receptacle, partly from the carpels ; in the Raspberry it is from the middle 



