PHANEROOAMIA. 233 



492. We have seen that fertilization of the germ-cell 

 not only caused the latter to develop into a plantlet, but 

 excited the tissues of the ovule to a growth which they 

 would not have made otherwise. This excitation of growth 

 extends much further than the ovule; it commonly causes 

 the ovary to undergo considerable changes, and in some 

 cases even parts of the perianth or the stem which bears 

 the organs of the flower. These changes give rise to the 

 fruit of Angiosperms. 



493. The changes which most frequently take place in 

 the growth of the fruit are such as (l) an increase in the 

 number of ovule-chambers by the formation of false par- 

 titions, or (2) a decrease in their number by the oblitera- 

 tion of some; (3) the growth of wings or prickles upon the 

 exterior of the fruit; (4) the thickening and formation of 

 a soft and juicy pulp; (5) the hardening of some portions 

 of the wall by the development of stony tissue; (6) the 

 thickening and growth of the calyx or receptacle. 



494. In cases where the walls remain thin and eventu- 

 ally become dry, the fruits are said to be dry — e.g., in the 

 bean; where the walls become thickened and more or less 

 pulpy, they axe fleshy — e.g., the peach. 



495. It is unnecessary here to describe the various kinds 

 of fruits. It is enough to point out that they all appear 

 to have to do with the protection or dispersion of the seeds 

 they contain. Thus the hard walls (as of nuts, achenes, 

 etc.) or the bitter pulp of some (as of certain berries) are 

 protective, while the sweet pulp (many berries, drupes, etc.) 

 and explosive capsules of others serve to distribute the 

 seeds. 



496. The particular structure of the flower, its position 

 on the plant, and its relation to other flowers in forming 



