18 PLANT LIFE 



circles is absent, as in the Croton flower. The third series, 

 consisting as a rule of a few or many thin stalks, bearing swollen 

 bodies at their tips, are the stamens or male organs ; the stalks are 

 known as the filaments, and the swollen bodies as the anthers, which 

 contain the pollen. The fourth and innermost circle consists of the 

 pistil, the lower inflated part of which is the ovary, containing the 

 ovules, which when fertilised become the seeds. At or near the 

 apex of the pistil is the stigma, through which the pollen tubes 

 penetrate to fertilise the ovules. The intervening part, when present, 

 between stigma and ovary is called the style. Flowers are 

 pollinated when the pollen from the anthers is transmitted, either 

 naturally or artificially, to the stigma. The act of fertilisation is 

 brought about by each of the pollen grains developing a tube which 

 grows through the stigma down the style to one of the ovules, 

 when its contents fuse with a special cell of the latter. The 

 functions of the exterior circles, calyx and corolla, may be con- 

 sidered as protective and attractive respectively ; while the stamens 

 and ovary are essential for reproduction. These latter may be 

 present in the same flower (hermaphrodite), or they may exist in 

 separate flowers (unisexual}. Flowers which possesses stamens 

 and not a pistil are called staminate or male flowers ; female or 

 pistillate flowers are those in which the stamens are absent. Some 

 plants bear both kinds of flower on the same individual and are 

 called monoecious; others bear them on separate individuals, as the 

 Date palm and Nutmeg tree, and are known as diwcious. 



Seeds. Every perfect seed contains an embryo, which is the 

 future plant in a rudimentary state. If the shell be taken off a bean 

 seed, for example, the following parts can be easily distinguished. 

 (1) two fleshy bodies placed face to face called cotyledons or seed- 

 leaves, known also as "nursing leaves ;" (2) a minute projection at 

 their base pointing upwards, called the plumule or future shoot ; 

 (3) a longer projection, also at their base, but pointing downwards, 

 called the radicle or future root. In germination the radicle 

 grows downwards, the cotyledons separate, and the plumule develops 

 upwards, the whole seedling living and increasing on the reserve 

 food stored in the nursing leaves until the roots are functionally 

 active, and the young parts and leaves above ground assume their 

 green colour. In other seeds, as cereals, palms, grasses, etc., the 

 embryo is very small, and is surrounded by a mass of tissue 

 (endosperm) which may be either of a mealy consistency (as in 

 Maize), oily (as in Hevea), or horny (as in palms). In these cases 



