XV] ROSACEA 147 



quincuncial. In many cases the imbrication is so slight, 

 however, that the margins must be regarded as merely in 

 contact (valvate). 



Then follow five equal petals, alternating with the 

 sepals and inserted just inside them, with even more 

 pronounced quincuncial aestivation, and spreading as the 

 flower opens as five delicate white or pink, more or less 

 obovate, and usually large and conspicuous organs, the 

 odd one being the anterior and with its one edge covered 

 and its other overlapping. 



Close inside the petals come numerous, about twenty, 

 stamens, curved inwards in the bud. 



Inserted at the base of the calyx-tube are the carpels, 

 which may be one {Prunus), or two to five {Gratcegus, 

 Rosa, Pyrus), or many (Rubus), and it is chiefly in the 

 numbers, degree of coherence, behaviour during ripening 

 of the carpels, and in certain relations of the carpels as a 

 whole to the calyx-tube, that these otherwise very similar 

 Rosaceous flowers differ among themselves. 



For instance, in Prunus (Fig. 43, A) the one carpel 

 becomes the single fleshy cherry, plum, &c., growing 

 quite beyond the cal3^x-tube as it ripens. 



In Rubus the numerous carpels develope into the 

 numerous small fieshy pips -each like a small cherry in 

 structure raised on the dome-like central part of the 

 floral axis, and again growing out beyond the calyx-tube 

 (Fig. 43, B). 



So that in both Prunus and Rubus we find the remains 

 of the sepals, petals and stamens at the base of the fruit, 

 owing to the growth of the latter beyond them. In the 

 flower, however, these organs are perigynous. 



In the Rose the carpels are inserted at the base of the 

 urn-shaped calyx-tube, and ripen to dry achenes, only the 

 long styles of which project at the top. Here the calyx- 



102 



