Abstract
This paper is a preliminary report of tripping experiments ot alfalfa (Medicago sativa) flowers. The staminal column and stigma of this flower were anatomically studied and the results obtained are as follows: In the transverse section of the staminal tube, the lower part of this organ is thicker than the upper part in width and the cell size of the former is larger than that of the latter. In the longitudinal section, the external cells of the staminal column are thicker in width and longer in length than those of the inner cells. Cuticule-like membranes were found on the stigmatic surface and granular fatty substances were secreted in the space between the stigma projection and the stigmatic membrane. However the structure of the stigma remarkably differs from what JOST has found on the stigma of Cytisus and Lupinus. The turgor pressure at the outer tissue of the staminal tube was higher 1.1 atmospheric pressure than that of the inner tissue. The motive power of tripping exists in the staminal column but not in the pistil. The pod setting of alfalfa was increased remarkably by artificial tripping compared with that of non-treatment, but when the standard petal was removed and tripped artificialy the fertilization of this plant was almost same to the case of non-treatment. The authors consider that the scope of tripping on the increased seed setting is in the confliction of stigma and standard petal. It is a problem to investigate minutely in future that the confiction of those organs produce results to either the scattering of pollen, the destruction of the stigmatic membrane or the both.
