Experiments on Plants 783 



June 20. They begin to sprout everywhere. 

 June 21. Already an evident difference. 



June 22. A. The numerous, very green, and very stiff sprouts 

 measure about 10 cm. 



B. Less numerous, less green; about 8 cm. 



C. Still less; about 6 cm. 



June 23. I cut all the shoots even with the barley seed; there are 

 76 in A, 36 in B, 25 in C. I put these shoots in the drying-oven and 

 dry them at 100 degrees for 2 days. 



After this time, each shoot in A weighs 8.8 mg.; each shoot in 

 B, 7.1 mg.; each shoot in C, 6.2 mg. 



Experiment CCCLI. June 11. Barley and cress on moistened 

 earth. 



A. Normal pressure. Bell of 1 liter. 



B. Air at a pressure of 12 cm. Bell of 6 liters. 



C. Air at a pressure of 8 cm. Bell of 8 liters. 

 The air is renewed every day. 



June 16. The shoots in A are very fine and vigorous; nothing 

 in B or C. 



June 20. B: a few radicles and white molds; C: only molds. 

 I bring B and C to normal pressure; the seeds germinate, those in C 

 being delayed during the first few days. 



I think it unnecessary to report a larger number of experiments; 

 each of the preceding experiments is really multiple because of the 

 number of seeds sown together. The following experiments cor- 

 roborate their results, which are certainly sufficiently clear. 



They permit us to draw the indubitable conclusion that the 

 lower the pressure, the less energetic and rapid is the germination. 

 I call particular attention to the results of Experiment CCCL, to 

 which the system of weighing gave especial precision. They show 

 that at normal pressure each of the barley shoots weighed more 

 than 8 milligrams, whereas at the pressure of 50 cm., they weighed 

 only 7, and at 25 cm., only 6. 



Furthermore, a much smaller number of seeds germinated at 

 low pressure than at normal pressure. It is rather difficult to un- 

 derstand the reason for this inequality, which was very evident in 

 each experiment; 'in the same experiment, CCCL, in which the 

 shoots were counted, we found 76 at normal pressure, 36 at 50 

 cm., and only 25 at 25 cm. 



. It is even now, therefore, quite evident that germination must 

 take place less rapidly and less surely, for seeds like barley, at high 

 altitudes than on the plain, if we assume that all conditions of 

 humidity, temperature, and the electrical state of the atmosphere 

 are similar. 



And now there appears the question which we had to settle 



