404 ROSACEA 



Ex. 209.— Examine "the flower of a strawberry. Make sections to illustrate 

 the shape and extent of the receptacle. 



Ex. 210. — Watch the growth of a strawberry from day to day until the fruit 

 is nearly ripe. Observe what becomes of the calyx, petals, and stamens. 



Examine the form and content of the carpels and the achenes which de- 

 velop from them. 



Make a vertical section of the nearly ripe 'fruit.' Note the distribution 

 of the vascular bundles in it. 



Ex. 211. — Compare a raspberry or blackberry flower with that of a straw- 

 berry. Watch the growth of the fruit after the flower fades, noting the 

 development of the little drupes from the carpels. 



Examine the structure of a young carpel and compare it with that of a 

 drupel. 



8. The genus Rosa includes the wild Dog-Rose {Rosa canina 

 L.) and several other indigenous species, as well as the many 

 introduced species and their hybrids and crosses much cultivated 

 as ornamental plants in the garden. 



The flowers are markedly perigynous. 



In the wild roses the calyx consists of five sepals ; the corolla 

 is polypetalous of five large petals, and the andrceclum possesses 

 numerous stamens. The receptacle is deeply-hollowed out like 

 that of the plum, but the upper part is constricted. The 

 gynsecium is apocarpous, and consists of many free carpels 

 inserted on the bottom and sides of the hollow urn-shaped 

 receptacle : the style and stigmas of the carpels protrude 

 through the narrow opening of the receptacle. After fertilisa- 

 tion the carpels develop into achenes with hard, bony pericarps, 

 and the receptacle which surrounds them becomes somewhat 

 fleshy and red. 



The ' hip ' of the rose is therefore a spurious fruit, which 

 consists of a scarlet or red receptacle inclosing the true fruit 

 (the achenes). 



Ex. 212. — Cut a vertical section of the wild rose. Note the form of the 

 receptacle, and compare it with that of a plum, cherry, or sloe. 



Observe the number, shape, and structure of the carpels ; also the position 

 of the sepals, petals, and stamens of the flower. 



