The spores, as in the heterosporous Pteridophyta, are of two kindsmicrospores (pollen grains) borne in microsporangia (pollen sacs) on special leaves (sporophylls) known as stamens, and macrospores (embryo-sac) borne in macrosporangia (ovules) on sporophylls known as carpels.
The male gametophyte is sometimes represented by a transitory prothallial cell;, the two male cells are carried passively down into the ovary and into the mouth of the ovule by means of the pollen-tube.
In such plants, the pollen grains are sometimes fihiform and not spherical in shape.
Its two pollen-masses in o, The twisted ovary.
Cross fertilization, or the impregnation of any given flower by pollen from another flower of the same species on the same or on another plant, has been proved to be of great - g advantage to the plant by securing a more FIG.
To facilitate the operations of such insects, by compelling them to move in certain lines so as to secure the due removal of the pollen and its subsequent deposit on the right place, the form of the flower and the conformation of its several parts are modified in ways as varied as they are wonderful.
For them the pollen is an attraction as food, or some other part of the flower offers an inducement to them for a like object.
Havingattained its object the insect withdraws, taking the pollen-masses, and visits another flower.
Pyramidalis, the two pollen-masses originally placed parallel I I diverge from the base like the letter V.
The anthers shed their pollen into this groove, either of themselves or when the pistil is shaken by the insertion of the bee's proboscis.
The eggs are deposited in the ovary-wall, usually just below an ovule; after each deposition the moth runs to the top of the pistil and thrusts some pollen into the opening of the stigma.
Bees store honey and pollen to serve as food for their young.
The conclusion at which he arrives is that the pollen is not in all flowering plants necessary for impregnation, for fertile seeds can be produced without its influence.
Botanists were for a long time content to know that the scattering of the pollen from the anther, and its application to the stigma, were necessary for the production of perfect seed, but the stages of the process of fertilization remained unexplored.
POLLINATION, in botany, the transference of the pollen from the stamen to the receptive surface, or stigma, of the pistil of a flower.
Species of Cactaceae), or the style bends so that the stigma is brought within the range of the pollen (e.g.
The sulphur-like pollen of the pitch pine soon covered the pond and the stones and rotten wood along the shore, so that you could have collected a barrelful.
A beekeeper, seeing the bee collect pollen from flowers and carry it to the hive, says that it exists to gather honey.
Another beekeeper who has studied the life of the hive more closely says that the bee gathers pollen dust to feed the young bees and rear a queen, and that it exists to perpetuate its race.
A botanist notices that the bee flying with the pollen of a male flower to a pistil fertilizes the latter, and sees in this the purpose of the bee's existence.