250 MORPHOLOGY OF THE ANGIOSPERMS 



plex nature. It is receptacular only in those ovaries with invaginated 

 receptacles. The fleshy sheath of the rose hip is receptacular in its basal 

 part, appendicular in its distal part. 



Among the Rosaceae, the Pomoideae have commonly been cited as 

 showing inferior ovaries in which the receptacle takes a prominent 

 part; the fleshy outer part of the apple and pear has been called cauline. 

 But comparative studies of the floral anatomy of the Rosaceae show that 

 this part of the fruit consists, morphologically, of the fused bases of the 

 outer appendages, that it is morphologically homologous with the base 

 of the hypanthium in Fragaria, Rubus, Agrimonia. 



Some varieties of roses and pears frequently bear proliferating flowers 

 in which a second flower grows from the center of the first. And, in 

 some varieties of apples, the flower buds of scions grafted into vigorous 

 seedlings develop into proliferating flowers and, rarely, fruits. Longi- 

 tudinal sections of these proliferated flowers and fruits show, in their 

 gross structure, evidence of the nature of the receptacle in these genera 

 (Fig. 96). In Rosa, the vascular cylinder spreads out into the base of the 

 fleshy cup, which bears the perianth and stamens on its rim, then dips 

 down into the central cavity, contracting, and rises from the base into 

 the pedicel of the secondary flower, above which its form is repeated. 

 All appendages may be present in both flowers, with the upper stele 

 arising between the carpels of the lower flower. In the pear, the vas- 

 cular cylinder extends directly up through the center of the flower, 

 without the spreading and invagination characteristic of the rose, and 

 into the pedicel of the second flower, where it follows a similar course. 



The flower buds of the apple scions develop branchlets that show 

 stages transitional from typical flowers to leafy twigs. Some branchlets 

 are flowerlike below, with sepals and petals, and leaves take the place 

 of carpels; others are flowerlike throughout, but have the tip of the 

 receptacle extending through the center of the carpel whorl, as a foli- 

 aceous twig. The anomalous structure of these flowers is the result of 

 the grafting process and the stage of development of the flower buds 

 when they became dormant. The grafting transferred the dormant buds, 

 with flower primordia at different stages, from a slow-growing, fruiting 

 branch to a vegetatively vigorous seedling. The primordia of floral 

 appendages that were well formed in the bud continue development 

 as floral organs; appendages still in early primordial stages develop as 

 foliaceous appendages. The flower bud in which, as dormancy began, 

 all the appendages had attained early primordial form, continued de- 

 velopment as floral appendages when growth of the scion began. If the 

 apex of the receptacle still retains a terminal meristem at this time, it 

 may build a leafy stem in the center of the flower, between the carpels 

 (Figs. 96 and 97). 



