288 PROCEEDINGS OP THE ACADEMY OF [1884. 



pistil, is able to carry up the tube with it," so that when the 

 resistance is removed, " the elastic stamens [filaments] draw the 

 tube down again," must therefore be given up. The expansion 

 of the arms of the style is not concerned in the process, for this 

 does not commence until after complete protrusion. 



As the filaments iu the Thistle tribe are sensitive to the touch, 

 in some Centaureas strikingly so ; as these are not stretched in 

 Centaurea, biit are usually bowed outwardly, and as they contract 

 upon the touch of a bristle or of a visiting insect, the first ques- 

 tion is whether the same may be the case, in some degree, in Sun- 

 flowers. My essays to determine this were made too late in the 

 season to be decisive. But in some flowers, on touching two 

 adjacent filaments with a bristle thrust into one side of the corolla, 

 the column moved promptly toward that side, moving through 

 fifteen or twent}' minutes of arc, very much as it will in a Cen- 

 taurea. I did not succeed in causing the five filaments to act 

 together, so as to produce any observable retraction. That this 

 retraction normally takes place without extraneous irritation, is 

 certain, commencing and commonl}' being completed on the 

 second day after full anthesis ; and equally in flowers shielded 

 from the visits of insects. 



In Sunflower-heads taken into a room and kept from bees, the 

 pollen, pushed out of the tube through the chinks betweeu the 

 anther-tips, or later borne on the brush of the (as yet) unopened 

 style-branches, is borne aloft, exposed to the bumblebees which 

 in the garden fi-eely visit them. Prof. Meehan states that 

 " honey -gatherers seldom resort to them," but I find that in our 

 grounds these were much the most frequent visitors. These were 

 passing from head to head and from plant to plant, inserting 

 their proboscis into the corolla-tubes in succession, beginning at 

 the circumference with the older flowers having expanded and 

 receptive stigmas, and proceeding to the pollen-loaded ones 

 witliin. It is easy to see that pollen is abundantly transported 

 from one head and one plant to another, and that it is carried 

 from flowers which could not possibly be self-fertilized until the 

 next day, and unlikely to be so then, to those the expanded 

 stigmas of which are only then receptive. Prof. Meehan " may 

 sa}^ emphatically that these arrangements favor self-fertilization," 

 but that is not the conclusion which I should draw from his own 

 illustrations any more than from my own. 



