68 PLANTS 



fertilization. Sometimes all the tissues of a flower cluster are 

 involved, more frequently the receptacle or calyx, but always 

 the ovary. The structures become enlarged and fleshy or 

 indurated and modified in various other ways. The resulting 

 structure or organ is called a fruit and its function always has 

 relation to the function of the seed. 



150. With the ripening of the seed the plant seems to have 

 fulfilled the object of its existence and soon dies, or if it is not 

 an annual it becomes dormant until the following season, when 

 another period of growth is closed by the ripening of the fruit. 

 Occasionally the fruit is not matured until the following season, 

 in which case the activity of the plant during the first season 

 is devoted to the storing up of reserve food, which is then 

 used in the development of the fruit during the second 

 season. 



151. The distinction between seed and fruit, then, lies in 

 this, that the seed is only that part which develops from the 

 ovule, while the fruit includes the seed and consists besides of 

 the modified ovary and frequently other adjacent parts of the 

 flower, which finally together constitute the seed-containing 

 organ of the plant. 



152. Simple fruits are either fleshy or dry, and the latter 

 are either indehiscent or dehiscent, hence the following classes 

 of fruits are recognized: 



153. A berry is a fleshy fruit composed wholly of the peri- 

 carp, or of the pericarp and the adherent calyx-tube. 



154. The drupe, or stone fruit, is also a fleshy pericarp, the 

 inner layer of which is stony. 



155. The pome is a fleshy fruit derived from the concave 

 receptacle which encloses the dry papery pericarp. 



156. An achene is a dry indehiscent fruit derived from a 

 simple pistil and containing only a single seed. 



157. A caryopsis resembles an achene, but has the seed coats 

 intimately united with the walls of the ovary. 



