HARRIS AND k'UCHS: OBSERVATIONS ON POLLINATION. 27 



turned toward the stamen or pistil. Even in the case of large 

 insects, such as Bombux, it would seem that the probability that 

 the stigma will be supplied with pollen from the large stamen 

 exclusively is very small. It seems improbable that S. rostra- 

 turn should depend exclusively upon such an uncertain method 

 of pollination as the projection, by the jarring of a stamen, of 

 a puff of pollen upon the side of an insect, and the subsequent 

 transfer of this pollen to the stigma of a flower of a different 

 type. Of course, it is not improbable that a part of the pollen 

 is furnished by the large stamen, as suggested by Professor Todd, 

 but that fertilization should be effected exclusively by this means 

 seems highly improbable. 



The pollen from the large stamen has been shown to be 

 fertile in a certain number of cases, but unfortunately oppor- 

 tunity was not offered for experiments on the fertility of pollen 

 from the small stamens. A rather hasty microscopic examina- 

 tion of fresh, unstained pollen from the large and small stamens 

 reveals no very striking difference in form. 



In C. marilandica, Meehan" found that the large, strong stamens 

 on each side of the pistil served only as a platform upon which 

 the insect could rest while procuring the pollen from the small 

 stamens. He found that the lower stamens, while filled with 

 pollen, did not dehisce of their own account, nor were they 

 opened by the insect. 10 



9. Meehan, Thomas, loc. cit. 



10. It must be stated tbat in a later paper [Robertson, Charles: Flowers and Insects, V. 

 Bot. Gaz., vol. XV, No. 8, pp. 199-204], Charles Robertson does not give the same results as those 

 found by Thomas Meeban. Robertson says : " Two long stamens, one on each side of the style, 

 furnish pollen for cross-fertilization. They have inflated anthers which probably have a bel- 

 lows-like action, like the long stamen of Solanun rost r atum and Rhexia virginica." Meehan 

 states expressly in his paper that in case of C. marilandica he was sure no pollen was ejected, 

 as Todd found for 8. rostratum, since in the flowers, which were covered with a gauze bag, the 

 membrane at the apex was never ruptured when the stamens were ready to fall. Rebertson 

 describes the method of extracting the pollen in C. chamcecrista in a way which is essentially 

 the same as Todd gives for 8. rostratum. He then says, in speaking of ('. marilandica : " Four 

 small stamens furnish pollen for the visitors. Bumblebees milk the pollen out of these, using 

 their jaws, as in the case of cTuzmatcrista." Meehan says : " Nor was there any draw-out of the 

 pollen, as observed by Professor Todd. It is abstracted solely through the pores ; and, although 

 I could see no evidence that such was actually the case, I suspect that fertilization could only 

 occur through some of this extracted pollen escaping from the insect to the stigma." It must 

 be noted here that the method which Meehan describes for the method of opening of the anthers, 

 the pollen being "abstracted solely through the pores," does not agree with the method de- 

 scribed by other observers. Leclerc du Sablon, in a paper, " Recherches sur la Structure et la 

 Dehiscence des Anthers," in vol. I of the seventh series of Annales des Sciences Nouvelles, dis- 

 cusses the anatomical modifications of the anther walls, by which dehiscence is secured. His 

 observations cover Cassia cremophilia ami Solanum (sp. ?) His observations do not cover 

 a sufficient number of species to make them of the greatest value in deciding the present points. 

 The author presents, in a condensed form, his results in: Note sur la Dehiscence des Anthers, 

 La Belgique Horticole, vol. XXXIV, pp. 148-150, 1884. Robertson says, in speaking of the cen- 

 tral of the three long stamens: "Bees, no doubt, force the pollen out of this as they do from 

 the short stamens." Meehan says : " I watched a mass of plants containing eighty-eight fiower- 

 stems on the :30th of July, and the same lot for an hour on the 6th of August, but saw no at- 

 tempt to get pollen from the longer anthers or to use them in any way but as a platform. It 

 would indeed be hardly possible for the bee to stand anywhere so as to get power to pierce the 

 apical membranes of the longer stamens. When the flower matured and the anthers were 

 ready to fall they were examined — the four short ones were empty sacs — the three lower ones 

 proved that they had not served any purpose to the bees, for they were full of pollen." 



