252 



STRUCTURE AND VITAL PROCESSES OF PLANTS 



bulbs, the Lotus plant by the branches of its rhizome, the 

 Bladderwort by detached segments of its stem, the Bryophyllum 

 by sprouts rising from its leaves, etc. In all these cases some 

 parts of the plant, other than its floral parts, detach themselves 

 from the mother-plant and become new independent plants. 

 Tliis kind of reproduction is called vegetative, as compared with 

 sexual reproduction by means of flowers and seeds. 



A. The Parts of the Flower and their Structure. 



1. Parts. — The flower is a short shoot with its leaves 

 arranged in whorls or spirals. A complete flower has four whorls 



of leaves, which from outside to the centre 

 are called sepals (forming the calyx), 

 petals (forming the corolla), stamens, and 

 pistils. (The stamens are often in two 

 whorls, as in the Glory Lily, sometimes 

 also in more than two whorls, as in the 

 Lotus; sepals, petals, or pistils are some- 

 times also in more than one whorl.) If 

 one of those four leaf-whorls is absent, 

 the flower is called incomplete. 



The function of each of the four kinds 

 of floral leaves is different. The two ex- 

 ternal rings have to protect the internal 

 ones in their unripe state. The corolla, 

 serves as a means for the attraction of 

 insects, inasmuch as it is vividly coloured. 

 The two internal rings, again, are the 

 organs of sexual propagation, the stamens 

 producing pollen, and the pistils seeds. 

 Hence the calyx and the corolla are the unessential, but stamens 

 and pistils the essential parts of a flower. 



'2. Incomplete Flowers. — On(} or even both of the floral 

 envelopes may Ije absent. Such a Hower is called monochlamy- 

 deous, if there is only one envelope, as in Castor; and aclilamy- 

 deous, if botli are al)sent, as in Pepper. If one of the essential 



Fig. 231.— The parts of 



a complete Hower: calyx, 



corolla, stamens, and 



pistil. 



