CHEMISTRY: S. J. BATES 
363 
To illustrate the advantages of germinating Oenothera seeds under 
experimental conditions over the old practice of sowing upon earth 
I will give the results for a problem as attacked under the old and new 
method. In 1914 I germinated on earth seeds from an Fi hybrid plant, 
13.35ac, of the cross 0. franciscana X 0. biennis. A sowing of 819 
seed-Kke structures produced a culture of 402 seedHngs, a germination 
of about 50%. The culture was grown partly to test the inheritance 
of a character (red coloration of the papillae on the stems and ovaries) 
present in franciscana and absent in biennis. This character was fully 
dominant in the Fi of this cross and in its reciprocal. It seemed reason- 
able to expect that a proportion of the plants in the F2 generation would 
present the clear green stems and ovaries (recessive) of biennis, but I 
found no plants of this t3^e in the culture of 1914. This winter (1915) 
I germinated in Petri dishes seeds from the same Fi hybrid plant, 13.35ac, 
and obtained 761 seedlings from about 921 seed-like structures, — a 
germination close to 82%. The new method had raised the proportion 
of germination more than 30%. Of the 761 seedHngs I was able to 
bring 748 to rosettes, the 13 which died probably belonging to a small 
group of etiolated dwarfs difficult to grow. It becomes a matter of 
interest to see whether or not in this culture of 1915 a group of green- 
stemmed plants will appear. 
1 Renner, O., Befruchtung und Embryobildung bei Oenothera Lamarckiana und einigen 
verwandten Arten. Flora, Jena, 107, 115 (1914). 
2 De Vries Hugo, The Coeflficient of Mutation in Oenothera biennis L. Bot. Gaz., Chi- 
cago, 59, 169 (1915). 
THE OSMOTIC PRESSURE OF THE IONS AND OF THE UNDIS- 
SOCIATED MOLECULES OF SALTS IN AQUEOUS SOLUTION 
By Stuart J. Bates 
CHEMICAL LABORATORY, THROOP COLLEGE OF TECHNOLOGY. PASADENA 
Presented to the Academy, April 27, 1915 
The concentration of the ions (G) and that of the undissociated mole- 
cules (Cu) are involved in the equation, C- / Q = K, expressing the 
appKcation of the law of mass-action to solutions of electrolytes. 
Hence the large divergence from this law which strong electrolytes ex- 
hibit may be due to the behavior of the ions, to that of the undissoci- 
ated molecules, or to that of both. This so called anomalous behavior 
may be simply expressed by saying that for one or for both of these 
molecular species van't Hoff's law, n = CRT, where H is the osmotic 
pressure, C is the concentration in mols per unit-volume, R is the gas- 
