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Show 88 HETEROSTYLED DIMORPHIC PLANTS. CHAP. III. and this was a very short one. To make su~e that the pollen was good, I took in this case, and In most of the other cases pollen either from the same anther 01~ from the sam: flower, and proved it to be good by placing it on the stigma of a short-styled plant, and found numerous pollen-tubes emitted. . Thirdly. Repeated last experiment, and placed ownform pollen on all :five stigmas of a long-st~led flowe~; after nineteen hours and a half, not one single grain had emitted its tube. Fourthly. Repeated the experiment, with the same result after twenty-four hours. Fifthly. Repeated last experiment, and, after leaving pollen on for nineteen hours, put on ~n additional quantity of own-form pollen on all five stigmas. After an interval of three days, the stigmas were exa1nined, and, instead of being discoloured and twisted, they were straight and fresh-coloured. Only one grain had emitted a quite short tube, which was drawn out of the stigmatic tissue without being ruptured. The following experiments are more striking :Sixthly. I placed own-form pollen on three of the stigmas of a long-styled flower, and pollen from a short-sty led flower on the other two . stigmas. After twenty-two hours these two stigmas were discoloured, slightly twisted, and penetrated by the tubes of numerous pollen-grains : the other three stigmas, covered with their own-form pollen, were fresh, and all the pollen-grains were loose ; but I did not dissect the whole stigma. Seventhly. Experiment repeated in the same manner, with the same result. Eighthly. Experiment repeated; but the stigmas were carefully examined after an interval of only :five hours and a half. The two stigmas. with pollen from a CHAP. III. LINUM GRANDIFLORUM. 89 short-styled flower were penetrated by innumerable tubes, which were as yet short, and the stigmas themselves were not at all discoloured. The three stigmas covered with their own-form pollen were not penetrated by a single pollen-tube. Ninthly. Put pollen of a short-styled flower on a single long-styled stigma, and own-form pollen on the other four stigmas; after twenty-four hours the one stigma was somewhat discoloured and twisted, and penetrated by many long tubes: the other four stigmas were quite straight and fresh ; but on dissecting them I found that three pollen-grains had protruded very short tubes into the tissue. Tenthly. Repeated the experiment, with the same result after twenty-four hours, excepting that only two own-form grains had penetrated the stigmatic tissue with their tubes ·to a very short depth. The one stigma, which was deeply penetrated by a multitude of tubes from the short-sty led pollen, pre sen ted a conspicuous difference in being much curled, half~ shri veiled, and discoloured, in comparison with the other four straight and bright pink stigmas. · I could add other experiments; but those now given amply suffice to show that the pollen-grains of a short-sty led flower placed on the stign1a of a long., styled flower emit a multitude of tubes after an interval of from :five to six hours, and penetrate the tissue ultimately to a great depth; and that after twenty-four hours the stigmas thus penetrated change colour, become twisted, and appear half-withered. On the other hand, pollen-grains from a long-styled flower placed on its own stigmas, do not emit their tubes after an interval of a day, or even three days; or at most only three or four grains out of a multitude emit their tubes, and these apparently never penetrate the : |
