POLLEN. 



73 



sometimes wanting ; when present it proceeds from the ovary, 

 and. bears the stigma on its summit; it is usiuilly Ions: and 

 slender, of a cylindrical form, consisting of bundles of fibers, 

 which transmit to the ovules, from the stigma, the fertilizing 

 pollen. The stigmais the continuation of the cellular tissue in 

 the center of the style. The stigma is always present ; if the 

 style be wanting it is placed upon the germ, and said to be ses- 

 sile^ as in the tulip. The stigma is various in size and form : 

 sometimes it is a roimd head ; sometimes hollow and gaping, 

 more es]3ecially when the flower is in its highest perfection ; it 

 is -generally downy, and always more or less moist, with a 

 peculiar viscid fluid. 



a. Fig. 87, A, represents the pis- Fig. 8/. 



til of the Cy noglossum ; style cylin- 

 dric, stigma depressed or flattened 

 at the top ; four ovaries, contain- 

 ing rudiments of seeds. B repre- 

 sents the pistil of the Tournefortii, 

 stigma Iiemispherical, sub-sessile, 

 surrounded witli a glandular hood. 

 C represents the pistil of the 

 Helitropium ; a, four ovaries ; b, a 

 short style ; c, a conical, four-part- 

 ed stigma. D represents a pistil 

 of the genus Cucumis; a is the 

 ovary adhering to the calyx ; b, 

 three abortive stamens ; c, cylin- 

 dric style ; d, three-lobed stigma ; 

 E, pistil of the genus Rumex ; a <i, 

 plumose stigmas, with three car- 

 pels at the base. 



81. 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. Tliis discharge of 

 pollen is owing to the formation of a tissue of fibers from the 

 cellular lining ; which fibers, by being coiled or interwoven, 

 form minute springs that by their mechanical force open the an- 

 ther and scatter the pollen. The pollen is very curiously form- 

 ed ; although appearing like little particles of dust, upon exam- 

 ining it with a microscope it is found to be composed of innu- 

 merable organized corpuscles. These, though usually yellow, 

 are sometimes white, red, blue, e^c. They are oblong in the 

 Umbelliferous plants, cjlohular in the Syngenesious, and trian- 

 gular in some others. In some their surface is smooth, in others 

 armed with little points. They are connected together by mi- 

 nute threads, as in the honeysuckle, &c. These particles of 

 pollen when 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. 



.«tigma— /7. Explain Fig. 87.— 81. Pollen. 



4 



