12 
reaction. It seems of special interest to determine here the degree of 
acidity, since the amount of enzyms of importance in the curing and 
sweating process may be decreased by acids.! 
ACID CONTENT IN DIFFERENT PARTS OF THE TOBACCO PLANT. 
The free acid of the juice was titrated in the usual way by one-tenth 
normal soda solution and calculated as free malic acid. Although in 
reality this acid is present as an acid salt and not as free acid, it 
makes no difference as to the number of unneutralized carboxyl groups, 
and the data obtained can serve for comparison. The juice was pre- 
pared by grinding the objects with the aid of some pure quartz sand 
and pressing the pulp through thin flannel. The juice of the leaf had 
to be mixed, however, previously to titration, with an equal volume of 
strong alcohol to precipitate suspended chlorophyll grains, otherwise 
the point of neutralization could not be observed with sufficient preci- 
sion on blue litmus paper, still less distinctly on violet litmus paper. 
Filtration, after the addition of the alcohol, was not found necessary 
previous to the titration. 
The amounts of free acid in the different organs are, of course, sub- 
ject to variation within certain limits, according to the atmospheric 
conditions and the influence of direct sunlight. Thus the writer has 
observed with the flowers of /pomeca triloba that warm weather with 
bright sunshine diminishes the acidity, while cool and rainy weather 
increases it, whereby the blue flowers turn red; and further, the acid- 
ity is greater in the morning than in the evening, which the writer 
also observed in the case of tobacco. The custom of harvesting tobacco 
on bright, sunny days has therefore a sound physiological foundation. 
The following data were observed: 
| | 
c.c. B, soda’ Per cent 
solution | of tree 
Part of plant. pes by| malie acid 
He c.c.juice in juice. 
ONTO OLS patetetatalatolata =latatataialaralafetotaratetaataratera(atecstarstaetaletetatetsiate ie tetom elateratatatctertortateiee anaes | _ 9.5 | 0. 033 
Pith 255 oheke ot inst ore ace eee dWasinis Ua ae ee ade Se eae Lee ee ee 8 - 052 
Baek 22a Se Sates crete Se TSE OHSS SE re eR eee ore 1.4 - 092 
Midribyof leat (evening) oo emt eter Ss tet elam eae eal ee ee ee oer 1.6 - 105 
Midribsof leaf i(@vening) =: sanssasc ase eee eee ea aera Hine Seer ee eee 1.5 - 098 
Midrib of leaf:(morning)...-25-2eecaniseass tee eae ene ease ee ee 2.1 - 138 
Lamina of:ripeleat a2. ss 556 2 See Boece ean oes ee ee eee eee OE en ees 4.4 - 294 
Lamina ofripe leaf se -Satssahocc cee ee ee ce Se OC Ee oe ea 4.2 -277 
yaminaxof young Suckerst -aece cae neta ee ae ele are ee eres 2.2 - 145 
Lamina/ot young Suckers :<2t22e.c-cea cece eee ene oe eee eee eee 2.4 - 156 
a Midrib and large side ribs removed. 
We learn from these numbers that the least amount of acid is con- 
tained in the small roots and in the pith; also that the lamina contain 
much more than the rib, and that the young leaves contain less than 
the ripe old leaves.’ 
' Certain fungi, as, for example, Oospora Nicotian, will grow on fermented tobacco 
only in the presence of some free organic (malic) acid (Splendore). This shows also 
in this respect an unfavorable effect of the acidity. 
These relations may differ in different plants. Thus Kraus has observed less of 
free acid in the leaf of Sempervivum than in the root. 
