PHANEROGAMIA. 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 
JSruit of Angiosperms. 
493. The changes which most frequently take place in 
the growth of the fruit are such as (1) 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 are 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 
