168 BOTANICAL GAZETTE [OCTOBER 
states that four substances might conceivably be present in the 
sample of plant tissue, and first determined their optical properties 
as follows: 
Alpha Beta | Gamma 2E. Sign 
Oxalic acid milgdeate 556s cs vhs £idde |r, 805 | £cs40 120° i 
Potassium binoxalate................ 1.415 | 1.545 | 1.565 65° = 
Potassium oxalate monohydrate....... 1.440 | 1.485 | 1.550 160° “ 
Calcium oxalate monohydrate......... 1.490 | 1.555 | 1.650 |Over 180° 2 
Examination of the sample showed two distinctly different 
crystalline substances to be present, one in rosettes of acute crystals, 
the other in nearly equant grains. The first proved to have the 
refractive indices characteristic of calcium oxalate as indicated, 
the second to have those of potassium binoxalate. The calcium 
salt occurs as aggregates of crystals, and therefore looks more prom- 
inent, but considering the large number of small grains of the potas- 
sium salt which are scattered around, it is evident that the potassium 
salt is present in the greater amount. Immersion liquids 1.490 and 
1.565 are most suitable for distinguishing the two, the potassium 
salt having one index much lower than the first, the calcium salt 
one much greater than the second. As no crystals were found to 
be present with gamma less than 1.560, or beta less than 1.540, it is 
to be inferred that neither oxalic acid nor neutral potassium oxalate 
is present, at least in significant amounts. 
TOTAL DISSOLVED OXALATES 
DEvEL has kindly consented to the inclusion in this paper of 
figures obtained by him for the soluble oxalate in a sample of foliage 
from the same group of plants from which these samples were ob- 
tained. His procedure was to boil the finely minced leaves in water 
for 1.5 hours, filter, make up the extract to definite volume, and in 
an aliquot determine the total soluble oxalate gravimetrically by 
precipitation as calcium oxalate, and after ignition, weighing a5 
calcium oxid. In the two samples of foliage examined he found 
oxalate equivalent to 2.06 and 1.96 per cent potassium binoxalate. 
The percentage of moisture on the samples was not reported, but 
the figures are for the fresh leaves. 
