ACCESSORY STRUCTURES OF FRUITS. 



433 



and bracteoles, the leafy structures which are present in the immediate vicinity of 

 the flowers, though not actually included in them. We may distinguish, perhaps, 

 amongst these accessory structures of the fruit, between such as arise from portions 

 of the perianth on the one hand, and such as are formed from bracts and bracteoles 

 on the other. The enumeration of these structures here, however, must be distinctly 

 limited to a few of the more commonly occurring. 



A curious form of fruit obtains in the Mulberry (Morus). The female flowers 



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Fig. 327. — The Hornbeam {Carpimis Betultis) in fruit. 



in this tree are arranged in little catkin-like clusters. Each flower consists of an 

 ! ovary inclosed in an inconspicuous four-leaved perianth. From each ovary a tiny 



nut arises; but the ripe fruit resembles a succulent berry rather than a collection of 

 j nuts. This is due to the fact that after fertilization, whilst the ovaries are developing 

 I into nuts, their perianths become distended and fleshy, altogether concealing the 

 I ovaries. Without a knowledge of the mode of development, the perianth might now 

 I be readily mistaken for the true fruit- wall (pericarp), and the nut for the seed 

 j In several species of Trefoil (e.g. Trifolium agrarium, badium, spadiceuvi) the 

 ! papilionaceous corolla is yellow. After fertilization this turns brown, dries up and 



forms a flying-arrangement for the small fruit within (cf. figs. 442 ^' ^' ^' *- ^). 



It very frequently happens that the Calyx is retained as an accessory to the 



