422 FARMERS' INSTITUTES. 



It is well known that any cause which produces a rank growth, does so at 

 the expense of fruitfulness, while if the growth is checked or the food sup- 

 ply cut off, all the energies of the plants are exerted in the production of 

 seed. This is a wise provision of nature as, while plants are young and 

 vigorous, there is slight need of immediate provision for the future, but 

 when they become old or weakened by disease or injuries, strenuous efforts 

 are made for the perpetuation of the species. 



Although all parts of the plant are requisite for its perfect development, 

 the flowers alone are directly concerned in the production of seed, and 

 hence may very properly be termed the reproductive organs. The essential 

 parts of the flowers, or those without which no seed can be produced, are 

 called stamens and pistils. The stamens generally consist of slender stalks 

 called filaments which bear on their tips the pollen sacs or anthers. The 

 pollen formed in the anther sells is generally a fine yellowish or brownish 

 powder. The pistil consists of a swollen portion called the ovary, which con- 

 tains the ovules, and tapers upward forming the style, at or near the end of 

 which is a point called the stigma. The stigmatic surface is generally 

 roughened and covered with a sticky fluid. The essential organs may be 

 grouped together in the same flower, they may be in different flowers on the 

 same plant, or even upon different plants. For the protection of the essen- 

 tial organs, nearly all plants have at least one row of covering leaves called 

 the calyx, and generally we find an inner row, the corolla. 



While the chief object of these parts is the protection of the stamens and 

 pistils, they are often large and of bright colors, and thus serve the impor- 

 tant purpose of rendering them conspicuous, that they may attract the atten- 

 tion of insects. In addition many flowers exhale strong odors for the same 

 purpose. 



When the pollen grains are ripe, the anthers burst, and the pollen is 

 transferred to the pistil. Sometimes it is carried to the stigma by the burst- 

 ing of the anther, or by movements of the stamens, but generally it is through 

 the agency of insects, or the wind. The sticky surface of the stigma retains 

 the grains, and they develop a slender tube which passes down through the 

 style to the ovary, and there enters one of the ovules. A portion of the 

 protoplasm of the pollen grain passes along the tube, and entering the ovule, 

 fertilizes the embryo. 



In order that all of the ovules may develop, a pollen tube must be sent 

 down to each one of them, and to make fertilization sure, a great number of 

 pollen grains are developed, one plant, wistaria, providing seven thousand 

 for each ovule. 



Such plants as require the aid of insects to convey the pollen to the stigma, 

 secrete a sweet liquid, called nectar, in some part of the flower. The insects, 

 attracted by the color or odor of the flower, enter and obtain the nectar. In 

 doing this they brush against the anthers and more or less of the pollen 

 adheres to them, going to the next flower the pollen is brought in contact 

 with the stigma. 



There is a wonderful adaptation in the parts of the flowers. Many blos- 

 soms are visited by moths which fly at dusk, and that they may more easily 

 find them they are generally white and are very odorous; flowers of a dull 

 yellow are never visited by beetles, but are fertilized by flies and bees ; some 

 plants bear flowers which never open, while others mature their pollen before 

 the petals expand, and in these cases they are self-fertilized. The majority 



