73 



STAMENS AXD PISTILS. 



fied. Fig. 83, A, shows the 

 pistil of the Cynoglossum. 

 The style is cylindric ; stig- 

 ma depressed or flattened at 

 the top. Four ovaries or ru- 

 diments of seeds. 



B, shows the pistil of the 

 Tournefortii. The stigma 

 is hemispherical, sub-ses- 

 sile, surrounded with a 

 ,VJ^^ glandular hood, a. C, shows 

 "^^ the pistil of the Helitropi- 

 um : a, four ovaries, two of 

 which only are visible in the 

 cut ; 6, a short style ; c, a 

 conical, four-parted stig- 

 ma. 



D, shows a pistil of the genus Cucumis ; a, is the ovary adhering to 

 the calyx; 6, three abortive stamens; c, cyhndric style; rf, three- 

 lobed stigmas. 



E, pistil of the Rumex genus ; a, a, plumose stigmas. 



Use of the Stamens and Pistils. 



In a former part of our Lectures, it was observed that the stamens 

 and pistils were necessary to the perfection of the fruit ; we ^vill 

 now explain to you the manner in which they conduce to this impor- 

 tant object; as" you are now acquainted with the different organs 

 and their names, you are prepared to understand the explanation. 



The pollen, which, in most flowers, is a kind of farina, or yellow 

 dust, is thrown out by the bursting of the anther, which takes place 

 in a certain stage of the flower. The pollen is very curiously form- 

 ed ; ahhough appearing like little pra-ticjes of dust, upon examining 

 it with a microscope it is found to be composed of innumerable or- 

 ganized corpuscles.* These little bodies, though usually yellow, are 

 sometimes white, red, blue, &c. In order to observe them well, it is 

 necessary to put them upon water ; the moisture, by swelling them, 

 renders their true form perceptible. They are oblong in the Um- 

 belliferous plants, globular in the Syngenesious, and triangular in 

 some others. In some their surface is smooth, in others armed with 

 little points. They are connected together by minute threads, as in 

 the honeysuckle, &c. These particles of pollen thus placed upon 

 water, swell with the moisture until they burst; a liquid matter is then 

 thrown out, and, expanding upon the surface of the water, appears 

 like a light cloud. 



The figure represents the pollen of seve- 

 ral different kinds of plants as seen under 

 a magnifier, when placed upon water. At 

 a, is a grain of pollen of one of the Mal- 

 ^ lows-hke plants, it is globular, hispid. At 



^ em. -p ^ b, the grain of the pollen is four-lobed. 



This belongs to the Orchis family. At r, is 

 the pollen of the Aster. At d, is the pollen 

 of the Hibiscus, globular, muricated. At e, 

 is the pollen of the Nasturtium ; angular, At f, is the pollen of the 

 honeysuckle. 



* Little bodies or particles of matter, 

 E.xplain Fig. 83— Use of the stamens and pistils— Description of the pollen. 



