CITRUS CULTURE IN CALIFORNIA -POLLINATION. 27 



The essential, or sexual, organs of the flower, the stamens 

 and pistils, are found inside the calyx and corolla, and it is 

 with these organs that the hybridizer is most concerned. The 

 stamens, or male organs, of the plant are usually several in 

 number, and are composed of an upper swollen portion, the 

 anther, which is borne on a more or less slender stalk called 

 the filament. In some flowers, as in those of the tomato, the 

 filament is very short, and in others is entirely wanting, the 

 anthers being borne at the base of the corolla. The very 

 numerous small, yellow, powdery grains of pollen, which con- 

 stitute the male fecundating elements, are borne in sacks in 

 the anthers. When the anther matures these sacks burst open 

 and the pollen is exposed. A quantity of this pollen must be 

 transferred, either by natural or artificial means, to the stigma 

 of the female organ in order to insure fecundation. The appli- 

 cation of pollen to the stigma is designated pollination, and 

 successful pollination that is, the application of pollen to the 

 stigma, followed by fecundation is termed fertilization. 



The pistil or pistils, which are the female organs, occupy the 

 center of the flower and are surrounded by the stamens. The 

 upper portion of the pistil is usually somewhat swollen and 

 more or less rough. It is on this portion of the pistil, known 

 as the stigma, that the pollen must fall to produce fecundation. 



In the majority of plants the stamens and pistils are pro- 

 duced in the same flower, as in the tomato and orange, but in 

 certain plants they are produced in different flowers on the 

 same plant, as in walnuts, castor beans, etc., or on different 

 plants, as in the willow, poplar, etc. 



In undertaking to hybridize plants artificially, it is well to 

 remember that in many plants the stamens and pistils when 

 in the same flower mature at different times a provision to 

 insure cross-pollination (the application of the pollen of one 

 flower to the stigma of another). In a large majority of such 

 cases the stamens ripen first, discharging their pollen before 

 the pistil is receptive. The most important feature in the work 

 of crossing is to exclude from the stigma all pollen except that 

 which it is desired to use. The prevention of self-pollination (the 

 transfer of pollen to the stigma of the same flower) in perfect 

 flowers that is, flowers containing both stamens and pistils 

 necessitates the careful opening of the flowers intended for 

 hybridization while they are still immature, and the cutting or 



