352 



A TEXTBOOK OF BOTANY 



(Ch. VII, 2 



that part which was already most nearly pulp-like in its 



structure. 



The fleshy fruits thus far described are all simple, that is, 



composed of a single pistil ; Ijut aggregate and multiple 

 fruits also occur. Thus, while in Strawfjerry 

 the pulp is the receptacle on which stand 

 the many dry akenes, in the nearly related 

 Raspberry the receptacle forms no part of 

 the fruit, which is made up of the many 

 separate aggregate carpels ripened to httle 

 drupes ; while in Blackberry both drupelets 

 and receptacle are included. Further, in- 

 stead of a single flower a cluster may form 

 a single large multiple fruit. This is the 

 case in the Mulberry (Fig. 247), in which 

 the pulp is chieflj^ calyx, and also in the 

 Pineapple, where not only the ovaries, but 

 also the bracts and main stem of a large 

 cluster of flowers ripen to the single coales- 

 cent fruit mass. A different form of 

 is that of the Fig, where the flowers are 

 a hollowed receptacle (Fig. 248). Somewhat 



in the nature of a multiple fruit also is 



the CONE (Fig. 249) of Pines, Spruces, 



and that family. This form of fruit 



belongs to the Gj^mnosperms, or naked- 

 seeded plants, which have no ovaries 



but usually bear their seeds on the 



bases of overlapping scales which col- 

 lectively make up the cones. 



The i)articular feature of pollination 



which acts as the stimulus to fruit 



formation is known. The pollen tube, 



as it reaches the embryo sac (jiage 278), 



contains normally two sperm nuclei, of ,, 



,., , , ,.,. ^, ' , iMii. 24S. — A Fig Iruit. 



which one always fertilizes the egg ce . (From Bailey ) 



Fig. 247. — The 

 Mulberry, made 

 up chiefly of the 

 ripened calyxes of 

 a cluster of flowers ; 

 X i". (From Figu- 

 rier.) 



multiple fruit 

 arranged inside 



