proceedings: botanical society . 295 



Experiinents were made to find the electrochemical decomposition 

 due to the electrolytic conduction of the strips of sulphide. A strip in 

 air (5.5 by 0.3 by 0.01 cm.) with silver-plated ends was soldered to 

 copper leads and put in a direct-current circuit. The initial current of 

 25 milliamperes was passed through it for nearly an hour without 

 visible change. The current was increased by steps of 50 milliamperes 

 at 10-minute intervals until with 200 milliamperes a discoloration of the 

 plating at the anode end was noticed. A further increase to 300 milli- 

 amperes completed the destruction of the silver plating at the anode end 

 and finally burned off the terminal, but before this happened a myriad 

 of little shinj' silver crystals appeared on the black surface of the sul- 

 phide. The appearance of these crystals was carefully studied under 

 the microscope, and it was found that they occurred even to within a 

 small fraction of a millimeter of the anode terminal. They appeared 

 in various forms, some of which suggested that they had been expelled 

 from the interior of the sulphide by considerable force. 



Discussion: The paper was discussed by Messrs. Buckingham, Hon- 



AMAN, BiCHOWSKY, SoSMAN, and BuftGESS. 



E. C. Crittenden, Corresponding Secretary. 



BOTANICAL SOCIETY OF WASHINGTON 



The 128th regular meeting of the Society was held at the Cosmos 

 Club at 8.00 p.m., Tuesday, April 2, 1918. There were 28 members 

 and 4 guests present. Messrs. L. L. C. Krieger, H. F. Bergman, 

 G. A. Meckstroth, and Wm.'N. Ankeney were elected to membership. 

 The following scientific program was given: 



Carleton R. Ball: The grain sorghums: a botanical grouping of 

 varieties cultivated in the United States (with lantern). There are two 

 chief centers of origin for the sorghums, Africa and India. The prin- 

 cipal groups cultivated in the United States are kafir, milo (including 

 feterita), and durra. All of these are of African origin. The kafir 

 varieties mostly were obtained from the native tribes in Natal, South 

 Africa. The Guinea kafir, however, probably was derived from the 

 West Coast of Africa, whence it was brought as food for slaves during 

 their long voyage to America. It is now cultivated in several islands 

 of the West Indies. The milo varieties probably are of Egyptian origin. 

 Very similar forms are grown in Egj^pt today under the names Durra 

 Beda (white) , Durra Saf ra (yellow) , and Durra Ahmar (brown) . Feter- 

 ita was derived from the British Egyptian Sudan. The durra varie- 

 ties, white and brown, probabh' came from North Africa, where they 

 are still found among the native tribes. These are the varieties known 

 in California as "White Egyptian corn" and "Brown Egj^ptian corn," 

 respectively. The white variet\^ has been grown in the Great Plains 

 area under the name "Jerusalem corn." The kaoHang varieties are 

 derived from North China and ^Manchuria. The different groups are 

 clearly separated by botanical characters. The speaker exhibited 

 charts showing by means of keys the classification of the sorghums. 



