28 
should be applied. An agricultural journal describes such a barn as 
follows: 
‘ 
The barn is what is called a ‘‘three-bent” shed. There are three rows of beams, 
one through the center and one on either side. A 2-inch steam pipe follows the out- 
side beams around the shed. - This is believed to be sufficient to supply the neces- 
sary heat to the whole building. The tobacco in the extreme outside of the shed 
rarely suffers from the pole sweat. The tobacco through the center, and especially 
that low down, is always the. worst affected, and the pipes are arranged to throw the 
most heat into that part of the building. Ifthe experiment proves a success in pre- 
venting pole sweat, the time is soon coming when artificial heat will be used entirely 
in curing tobacco, for the even temperature and moisture that can be obtained are 
just what is needed for a perfect cure. 
As the curing proceeds an alternating change from the moist to the 
dry condition of the leaves takes place, according to the atmospheric 
conditions. Practical experience has proved that a frequent change of 
this kind is desirable.’ This agrees also with the theoretical inference. 
There is more oxidase in the ribs than in the mesophyll, and by the 
alternate drying and moistening the evaporation from the surface 
causes a current of juice to pass from the ribs to the mesophyll cells. 
This migrating juice finally distributes most of the oxidase from the 
bundle sheath and sieve tissue uniformly through the leaf. It is there- 
fore desirable to have the ribs keep alive much longer? than the rest of 
the leaves, since deau and dry ribs would not support the process 
indicated. 
As long as all the cells of a leaf are alive a current of organic mat- 
ter—especially sugar, and also to a small degree, amido compounds— 
takes the opposite direction, namely, from the lamina to the ribs. Grad- 
ually this function stops, since a state of starvation sets in when the 
starch, in the form of sugar, has been transported to the stalk and 
consumed by respiration. The decrease of soluble albumin in the cur- 
ing process is much slower than the decrease of starch. Even after a 
fortnight a moderate amount is left, and with single cured leaves, even 
after four weeks, some traces of it were found in the tissues. 
DECREASE OF ACIDITY. 
It is an interesting fact that the acid reaction decreases in the lamina 
as the curing proceeds, as shown by the following table. For 200 sq. 
em, there was required the following amounts of one-tenth normal soda 
solution: : 
Uppermost | Lower 
Date. a | leaves. 
Cae C. C. 
AWM SUSH Ts Po ee Sac ee we a eee ce eee ST a 3.8 3.0 
AOS EG: Bears F55 5 ree lac he Sats ae a ap cee ne ge | 3.3 2.3 
AMOUSE V4 stk Bee Sa are ee ene on = a 2.5 a 
September 26 5san 25h ooees See ee ee ee eee ea ho pp es Berea 1.7 9 
'Report No. 62 (p.12), U. S. Department of Agriculture, by Marcus L. Floyd. 
This report also contains views on the best construction of the usual barns. 
“The midrib may remain alive for three weeks and over. 
