328 PEACTICAL BOTANY 



ovule is the seed. When any other structure is added the 

 result is the fruit. For example, if the ovary wall hardens 

 about the seed, as in the sunflower, we have the kind of fruit 

 called an akene. In the stony fruits, as the peach, the ovary 

 wall divides, the inner part produces a hard covering to the 

 seed, and the outer part produces a pulpy flesh. In an apple 

 the calyx is joined to the wall of the ovary, the seeds are 

 inclosed within ovary cavities, the ovary wall ripens into the 

 core, and the calyx ripens into the greater part of the apple 

 fruit. A transverse or longitudinal section of an apple or pear 

 will usually enable one to determine what part of the fruit is 

 the ripened calyx and what part is the ovary wall. In general 

 it may be said that the fruit is the seed plus anything else 

 that ripens with it. In plants such as the bean (Fig. 15), while 

 seeds are maturing the entire carpel grows and the ovary ripens 

 into the fruit known as the pod. (See Chapter IX for discus- 

 sion of the germination of seeds and the development of the 

 parts of the adult angiospermous plant.) 



301. The life cycle of angiosperms. The flowering plants 

 which we ordinarily see are the sporophytes, since they pro- 

 duce asexual spores. Angiosperm sporophytes are highly or- 

 ganized, with complex and divergent types of roots, stems, 

 and leaves, and living with almost every possible habit in 

 every possible region. So varied in form and habit are these 

 plants that no single type or few types can adequately repre- 

 sent them. 



The flower is primarily organized to produce asexual spores, 

 but later is also used for sexual reproduction. In fact so closely 

 related are these two reproductive stages that people some- 

 times erroneously speak of the stamen as the male structure of 

 the flower and the pistil as the female structure. No confu- 

 sion need arise with the stamen, since it is the microsporophyll 

 which produces the pollen grains. Later the pollen grain ger- 

 minates and produces the male gametophyte. The pistil offers 

 more difficulty, for although it first produces a megaspore, that 

 cell produces the female gametophyte within the ovule. The 



