It will be noticed that when a marked excess of flowers of one kind occurs one morning, a somewhat proportionate excess of the other type occurs the following morning. This is of course necessary if an equal number of the two types of flowers are to be produced and, to a certain extent, to be maintained on the same plant; and is to be expected from the alternate occurrence of the two types on opposite sides of the raceme.
The flowers open early in the morning and remain open from three to four days, depending somewhat upon the condition of the weather. Some which were covered with cheese-cloth “tents” were noticed to remain open almost a week. At the end of this period the corolla wilts and falls off, as does also the pistil. The flowers seem to partially close at night.
A limited series of experiments were made to determine if self-fertilization and cross-fertilization between flowers of the opposite type opening simultaneously on the same raceme are possible.[I]
The writers have not made sufficiently extensive observations to arrive at any general conclusions of value as to the comparative fertility of cross-and self-pollination, either between flowers on the same or different racemes, or between the flowers of different plants, but they have been able to obtain a limited series of definite results which may be of interest.
In making experiments to determine these points, all old flowers were removed from the plants in the afternoon or evening and the plants covered with a small “tent” of cheese-cloth. The cheese-cloth was of a mesh sufficiently small to prevent the access of any insects large enough to effect pollination, while large enough to allow a ready circulation of air and good illumination. The following morning pollination was effected between the flowers which had opened by tapping pollen from the large anther onto a clean glass slip and transferring it to the stigma of the same or another flower. The plant was then again covered and allowed to remain so, except when examined from time to time, until the corolla and pistil had fallen off. The following results were obtained from three plants upon which observations were made:
Plant I.
August 20. (a) Twelve stigmas pollinated with pollen from large stamen of the same flower.(b) Cross-pollination effected between two flowers which had opened on a raceme at the same time.
August 22. (a) Five of the twelve flowers had fallen off. (b) One flower had fallen off. The other seemed to be developing.
August 24. (a) Five ovaries with their corollas fallen off appeared fresh and healthy and seemed to be developing. Two more of the twelve had dropped off. (b) Remaining pod seemed to be thriving.
August 26. (a) Four of the five ovaries were clearly developing. The fifth appeared doubtful.