1884.] NATURAL SCIENCES OF PHILADELPHIA. 28T 



NOTES ON THE MOVEMENTS OF THE ANDROECIUM IN SUNFLOWERS. 



BY DR. ASA (iRAY. 



My attention was called to this subject by some observations 

 made by Professor Meehan, the substance of which is now printed 

 in the " Proceedings of the Academy' of Natural Sciences," pp. 200, 

 201, under date of July 15 of this year. My own study of the 

 subject was necessarily desultory and interrupted, and mainly too 

 late in the season for the most satisfactory investigation. My 

 object in sending this communication to the Academy, at this 

 time, is, in the first place, to thank Mr. Meehan for calling atten- 

 tion to a very obvious fact, which I had entirely overlooked, and 

 which those botanists (such as the late Hermann Miiller), who 

 have particularl}' attended to the adaptations for fertilization in 

 Compositne, were seemingl}^ not aware of. The fact referred to, is 

 the retraction of the anther-tube in Helianthus (and so, presum- 

 ably, in its near allies), somewhat in the manner of Gentaurea and 

 the Thistle tribe generally. In the second place, I wish to main- 

 tain -that this retraction in the sunflower is the result of automatic 

 or irritable shortening of the filaments, and not of the "elasticity 

 of the filaments." In other words, that those organs act in Sun- 

 flowers as they have for a long time been known to do in the 

 Thistle tribe, but with some difference. If I riglitly understand 

 Professor Meehan's account, he supposes that the antlier-tube is 

 carried up to its full height by the elongation of the style within, 

 its stigmatic apex pushing against the conniving anther-appendages 

 which close the orifice of the tube, and so stretching the filaments ; 

 and that the elastic shortening of the filaments pulls down the 

 anther-tube when the style has overcome this obstacle and pro- 

 truded. If this were so, the stamen-tube should be drawn down 

 at once upon overcoming the resistance. It is easy to test 

 this, by snipping off the anther-tips by sharp scissors. But when 

 I did this, no retraction followed. Moreover, on splitting down 

 anther-tubes at various stages of their growth, I found that only 

 at the last, and after the anther-tube had attained its full height, 

 was the tip of the stjde in contact with the anther-tips. Prof. 

 Meehan's idea that " the extension of the staminal tube is evi- 

 dently mechanical, and is due solely to the upward growth of the 

 stigma, which, partly it seems by the incurved points of the 

 stamens, and partly perhaps by the expansion of the arms of the 



