oe ee et. 
PLAN OF THE EXPERIMENTS. 4] 
hours. In laboratory water the growth was 16.9 mm. for the first 24 
hours and 5 mm. for the second 24 hours—a total growth of 21.9 mm. 
Pea cultures a week old were to outward appearance as good in one 
kind of water as the other, and the experiments were therefore carried 
on with the laboratory water, without any aey treatment, 
such as shaking it w ith carbon black. 
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6 AZ 
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YS. 
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Fic. 4.—Seedlings of culture 10, experiment C. 
Canada field peas, supplied by Prof. C. V. Piper (S. P. I. No. 19290), 
proved to be very easily handled in water cultures. Before germina- 
tion they were graded according to size and color (some had green, 
others yellow, cotyledons). A sufficiently large number of the same 
grade were germinated in moist sphagnum, so as to have enough 
seedlings for a second selection at the time of setting up the cultures. 
They were used when the primary root had attained a length of 4 or 
231 
