. Cyclopedia of American horticulture, comprising suggestions for cultivation of horticultural plants, descriptions of the species of fruits, vegetables, flowers, and ornamental plants sold in the United States and Canada, together with geographical and biographical sketches. Gardening. 1388 POLLEN POLLINATION then, is to be found a reason for the beauty and special- ization of external wall. In entomophilous pollen the elliptical form of grain predominates, but the general shape is extremely various; and the plants producing such pollen are usually provided with beauty of flower, fragrance, o
. Cyclopedia of American horticulture, comprising suggestions for cultivation of horticultural plants, descriptions of the species of fruits, vegetables, flowers, and ornamental plants sold in the United States and Canada, together with geographical and biographical sketches. Gardening. 1388 POLLEN POLLINATION then, is to be found a reason for the beauty and special- ization of external wall. In entomophilous pollen the elliptical form of grain predominates, but the general shape is extremely various; and the plants producing such pollen are usually provided with beauty of flower, fragrance, or other insect attraction. In order that the pollen which has been trans- ported to the stigma may be effective, it must be healthy. Experiments have shown that weak, poorly nourished orchard trees often produce ineffective pollen. The nature of the season may also have great influence upon its character, continued rains 1870. Pollen erains of Primula ob- conica (below) and salvia. Magnified. 1871. Pollen grains of Browallia. Magnified. 1872. Oddly marked Pollen grain of Schaueria flavicoma, Magnified. causing great losses by preventing the maturity of this product as well as by mechanical injury and by pre- cluding the winged carriers. Most plants have some special provision for the protection of the pollen against rain; that is, either by the closing of the flower under moist conditions, or by the location of the anthers in a sheltered tube, under projecting hairs, lobes, or other comlia appendages. The individual particles of pollen are in the form of delicate grains only readily visible in some quantity, as in powdery masses. At the time when they are set free, the grains are generally entirely distinct from one another, to be blown about by an accidental wind or carried by visiting insects. In some cases, however, the grains are bound together loosely or by means of delicate glutinous threads (Rhododendron); they may be closely united into 4's fheatb family); or the whole
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