174 Proceedings, 



establish a new center of distribution. Not a few plants have developed in 

 the course of the great struggle for supremacy special mechanical contri- 

 vances by means of which they themselves propel their seeds to a safe dis- 

 tance. Many of these adaptations are truly marvelous. Among them may 

 be mentioned the remarkable "catapult" of the witch hazel {Ramamelis), 

 the well-known bursting pod of the balsam or jewel-weed (Impatiens,) the 

 common Oxalia, the elastic siliques of many Cruciferce and the strange 

 squirting cucumber {Momordica) of northern Europe. The common tum- 

 ble-weed {Amarantus albus) and the Psoralea (especially argephylla) of our 

 western prairies are illustrations of a singular mode of seed distribution 

 where the whole plant is of globular growth and separating at maturity at the 

 surface of the earth, rolls to and fro before every wind, thus serving as a most 

 excellent "seeder." If enough has been said to suggest the instructive 

 field of study that here lies within easy reach of every student of botany or 

 evolution the purpose in view will have been attained. 



Conway MacMillan then discussed "Heliotropism." 



A brief discussion of the movements of the aerial plant-organs under 

 the influence of unequal lateral illumination, with explanations, according 

 to the various investigators (De Candolle, Frank, Pfeffer, etc,,) of the inti- 

 mate molecular changes upon which such movements are probably condi- 

 tioned. 



(This paper was published in full in the Popular Science MontJily for Sep- 

 tember, 1888.) 



Dr. A. F. Elliot presented some cones and leaves of the Sol- 

 dad pine of California. 



Dr. J. H. Sandberg was elected a member. 



April 3, 1 888. 



Fifteen persons present. 



A. S. Dimond was elected a member. 



Professor Dodge, of the section of Chemistry, continued the 

 subject presented one year ago, in a discussion of ''the purification 

 of water for domestic purposes, particularly filtration." 



First were considered the sources of contamination — cesspools, wells, 

 impure ice, etc. Citations of recorded cases were made to show the risks 

 run in using unpurified water. 



Secondly, several different modes of filtration were described, and sug- 

 gestions offered for filter making. The construction and points of advantage 

 of the following filters were pointed out: Pasteur's; the powdered coke 

 filter; the Hyatt filter. 



May 8, i888. 



Fifteen persons present. 



Chas. S. Fellows was elected a member. 



