200 



PROCEEDINGS OP THE ACADEMY OP 



[1884. 



July 15. 



Mr, Thomas Meehan, Yice-President, in the chair. 



Fifteen persons present. 



A paper entitled " The Geology of Delaware," by F. D. Chester, 

 was presented for publication. 



On Elasticity in the Filaments of Helianthus. — Mr. Thomas 

 Meehan remarked that in many composite flowers the pollen is 

 ejected from the apex of the staminal tube, and it became a matter 

 of interest to ascertain the mechanism by which this is accom- 

 plished. The flowers of compositse ai-e much frequented by pollen- 

 collecting insects. Honey-gatherers seldom resort to them. It 

 is difficult on this account to watch the flow of pollen in the open 

 air, as it is collected by the insects as fast as it appears. Some 

 flowers of Helianthus lenticularis^ Dougl., were gathered, and for 

 the purpose of study placed in saucers of 

 water in a room where insects could not dis- 

 turb them. In this way it was observed that 

 after the corolla tube had reached its full 

 length, very early the following morning the 

 staminal tube commenced to grow beyond 

 the mouth of the corolla, and by about 9 

 A. M. had extended to a distance of about one- 

 fourth the whole length of the corolla. The 

 pollen then commences to emerge through the 

 upper portion of the staminal tube, which, 

 the stamens narrowing, has the apices free. 

 During the day the pollen continues to pour 

 out, till by nightfall a large amount has 

 accumulated at the apex of the tube. A 

 floret at this stage of growth is represented 

 by fig. 1. The morning of the second day 

 the arms of the pistil emerge and commence 

 to expand, and at onqe the staminal tube 

 begins to descend, exhibiting at the end of 

 the second day the appeai'ance indicated by 

 fig. 2. By the end of the third da}^, the 

 staminal tube has retired entirely within the 

 tube of the corolla, and with the pistil, commences to wither. A. 

 careful examiuation shows that through the whole course the 

 column of united anthers remains entirel}' of the same length. 

 It is the filaments only which are elastic. These stretch fully 

 one-half their length. Thej^ ai-e attached to the tube of the 

 corolla at the inflated portion a short distance above the achene, 

 and extend to about midway between this point and the end of 

 the tubular portion at the base of the limb; but when the anther 

 tube is extended as described in fig. 1, tlie filaments occupy the 



