BOTANY: A. R. HAAS 
563 
spect (except that they contained no seedlings) and having the holes 
in the covers partially covered so as to obtain about equal amounts of 
evaporation in all the tumblers. A series of phosphate buffer solu- 
tions, of known hydrogen ion concentration, and checked by the use of 
the gas chain, were made up. Phenolsulphonephthalein (12 mgm. 
per 100 cc.) was used as indicator (3 drops to 10 cc. of solution). 
The indicator was added to a series of tubes containing the various 
buffer solutions whose PH+ value was known. ^ After the plants had 
grown for 8 days, 10 cc. of the water from each tumbler was run into 
a tube of the same diameter as those containing the buffer solutions 
and after adding 3 drops of the indicator, the CO2 was expelled by a 
stream of hydrogen (washed free from impurities). The hydrogen was 
allowed to run through each tube for one-half to three-quarters of an 
hour to be sure of expelling all the CO2. 
TABLE 1 
Results after CO2 was expelled 
Water from tumblers Water from controls 
containing roots without plants 
1. Ph+ 7.38 . 1. Ph+ 7.38 
2. " 7.38 2. " 7.38 
3. " 7.38 3. " 7.38 
Experiment 2. Seedlings with vigorous roots and with apparently no 
dead cells, were grown for 5 days in culture. The distilled water was 
different from that in Experiment 1. 
TABLE 2 
Results after CO2 was expelled 
Water from tumblers containing roots Water from controls without plants 
The water from 7 tumblers each PhH- 7.16 The water from 6 controls each Fs+ 7.16 
A similar experiment in glass tumblers was run for 19 days. During 
that time the cultures received no attention whatsoever. Analysis 
showed no increase of acidity, even though the roots were full of brown 
spots. 
The use of glass tumblers might be objectionable because of the pos- 
sible dissolving of the glass, resulting in the possible neutralization of 
any excreted acid, but in that event the controls ought to indicate an 
increased alkahnity. 
The experiment was then repeated, using large quartz dishes instead 
of glass tumblers. The covers were made of large sheets of filter paper 
impregnated and coated on both sides with a thin layer of high grade 
parafhne, melting point 60-62°C. Holes of the required size were cut 
out of the cover with a sharp cork borer. The cover was laid on the 
