500 proceedings: botanicai^ society 



axial forces exceeding 0.05 gram under regular operating conditions. 

 An auxiliary U-tube partly .filled with mercury, separates the oil in the 

 gage from the pressure to be measured and indicates any movement 

 of the piston. This manometer has a range of about fifty grams per 

 square-centimeter, hence the use of weights smaller than 50 grams is 

 avoided. 



Comparisons of the piston gage with the manometer, which were 

 made before the present rotating device was used, give 1.3031 square 

 centimeters at the efi"ective area or 1.1302 centimeter as effective 

 diameter at 25 degrees C, whereas direct measurements of the diameter 

 of the piston give 1.1298 centimeters. The results of the comparison 

 up to 15 atmospheres showed variations from the mean, due to both 

 gages combined, corresponding to 1.5 mm. pressure. Further compar- 

 ison at pressures above 15 atmospheres will be made. 



The gage described in this paper was exhibited and operated by the 

 authors at the close of the meeting. 



Discussion. — The paper was discussed by ISIr. White. 



S. J. Mauchly, Recording Secretary. 



BOTANICAL SOCIETY OF WASHINGTON 



I43RD MEETING 



The 143rd regular meeting of the Botanical Society of Washington 

 was held at the Cosmos Club, 8 p.m., April 6, 1920. Sixty members 

 and thirty-three guests were present. 



Under "Brief Notes and Reviews of Literature," Mr. F. L. LewTon 

 exhibited three specimens of the fruit of a large leguminous tree, Andira 

 excelsa HBK, known in Tabasco, Mexico, as "Macayo." The seeds 

 contain a poisonous alkaloid. They are used locally as a vermifuge 

 and purgative, but because of their poisonous nature, have been the 

 subject of several articles sounding a warning against the careless use 

 of them. The fruits are oval, 8-12 centimeters long, and grooved on 

 one side with a roughened surface resembling the convolutions of the 

 brain. 



Prof. A. S. Hitchcock read an illustrated paper on A botanical trip 

 to British Guiana. He stated that British Guiana has an area of about 

 90,000 square miles, extending back from the coast about 400 miles. 

 The climate is strictly tropical, the temperature at Georgetown varying in 

 summer from 82° at night to 88° in the day, and in winter from 78° 

 to 84°, F. The rainfall at Georgetown averages about 90 inches, distrib- 

 uted somewhat vaguely into two wet and dry seasons. In the interior 

 the distribution is nearly normal for Tropical America, the wet season 

 being from April to August. The vegetation is characteristic of the 



