The elements of botany for The elements of botany for beginners and for schools elementsbotany00gray Year: 1887 297. An ordinary polleu-graiu lias two coats; the outer coat tliickisb, but weak, aud frequently adorned with lines or bands, or studded with points; the inner coat is extremely thin and delicate, but extensible, and its cavity when fresh contains a thickish protoplasmic Huid, often rendered turbid by an immense number of minute particles that float in it. As the pollen matures this fluid usually dries up, but the protoplasm does not lose its vitality. When the grain is wetted it ab
The elements of botany for The elements of botany for beginners and for schools elementsbotany00gray Year: 1887 297. An ordinary polleu-graiu lias two coats; the outer coat tliickisb, but weak, aud frequently adorned with lines or bands, or studded with points; the inner coat is extremely thin and delicate, but extensible, and its cavity when fresh contains a thickish protoplasmic Huid, often rendered turbid by an immense number of minute particles that float in it. As the pollen matures this fluid usually dries up, but the protoplasm does not lose its vitality. When the grain is wetted it absorbs water, swells up, aud is apt to burst, discharging the contents. Bui when weak syrup is used it absorbs this slowly, aud the tough in- ner coat will sometimes break througii the outer aud begin a kind of growth, like that which takes place when the pollen is placed upon the stigma. 298. iSome pollen - grains are, as it were, lobed (as in Fig. 315, 316), or formed of four grains united (as in the Heath family, Pig. 317) : that of Pine (Fig. 318) has a large rounded and empty bladder-like expansion upon each side. This readers such pollen very buoyant, and capable of being trans- ported to a great distance by the wind. 299. In species of Acacia simple grains lightly cohere into globular pellets. In Mdkweeds and in most Orchids all the poUen of an anther-cell is compacted or coherent into one mass, called a Pollen-mass, ot PoLLiNiuM, plural PoLLiNiA. (Fig. 319-322.) ©J 319 ing Primrose, the three lobes as large as the central body; 317, of Kalmia, four grains united, as in of the Heath family; 318, of Pine, as it were of three grains or cells united; the lateral enijity and light. Fig. 319. Pollen, a pair of poUinia of a Milkweed, Asclepias, attached by stalks to a gland; moderately magnified. Fig. 320. Pollinium of an Orcliis (Habenaria), with its stalk attached to a sticky gland; magnified. 321. Some of tlie packets or partial pollinia, of wliieh Fig. 320 is made
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