440 University of California Piihlications in Botany [Vol. 5 



II. METHODS 



The illuminating gas supplied to the laboratories of the University 

 of California has the following composition by volume. 



Nitrogen 4.10% 



Oxygen 0.10 



Hydrogen 55.00 



Methane 26.30 



Ethylene 5.00 



Carbon dioxide 1.80 



Carbon monoxide 7.70 



In the experiments with Nicotiana the apparatus for subjecting the 

 flowers to certain percentages of illuminating gas and its constituents 

 consisted of five-litre bell- jars. In one case the bell- jar was fitted with 

 a ground-glass stopper and stopcock and was set in a large crystallizing- 

 dish so that the mouth of the bell-jar could be closed with a water seal. 

 Part of the air in the jar was then drawn off and the jar partly filled 

 wnth water, the volume of air Avas noted and the desired amount of gas 

 being experimented with was introduced through the stopcock. In 

 the other case a bell-jar was fitted with a ground-glass plate which 

 sealed up the open end completely, the seal being made air-tight with 

 vaseline. This bell-jar was fitted with two stopcocks and the gas being 

 experimented with could thus be easily introduced and an equal 

 volume of air simultaneously drawn off. In each of the experiments 

 a portion of the terminal or lateral inflorescence upon which were 

 seed capsules, open flowers and unopened buds was cut carefully from 

 the plant and the cut end of the stem placed as quickly as possible in 

 w^ater in a 250 c.c. Erlenmeyer flask and the whole placed under the 

 bell-jar. For each experiment a control was also kept in the open air. 

 During the course of the experiments the flowers were shaken at 

 frequent intervals to see if abscission had occurred. Flowering laterals 

 from one plant of Nicotiana Tahacum var. macrophylla purpurea 

 (U. C. B. G. 25/06) were used throughout. 



In the experiments to determine the comparative effects of the con- 

 stituents of illuminating gas upon floral abscission in this species of 

 Nicotiana the gases were prepared as follows: 



(a) Carbon dioxide — action of dilute c. p. sulfuric acid on pure 

 sodium bicarbonate. 



(6) Carbon monoxide — treating c. p. sodium formate with pure 

 cone, sulfuric acid and washing by bubbling through strong sodium 

 hydroxide solution. 



