15 
ripening stage the upper leaves may easily be broken or lacerated, thus 
leading to a considerable loss. 
The single-leaf curing, a process that seems to grow more and more 
in favor with the farmers in certain States, takes one-third less time 
than stalk curing, permits the harvesting of about double as many 
leaves as the curing on the stalk, gives a more uniform product, and 
permits the gathering of top suckers, which may form good wrappers.! 
The stalk is here longer in the field and continues to produce healthy 
leaves from the suckers. 
ENZYMOLOGY OF THE TOBACCO PLANT. 
The important physiological role of enzyms for every organism is 
well known. Some enzyms are found in all organisms, others only in 
a few, and some may even occur only in one. Three physiological 
groups of enzyms can be distinguished: (1) Such as are most inti- 
mately and directly connected with the nutritive processes, as diastase 
and proteolytic enzyms; (2) suchas bring on coagulation—the clotting 
enzyms, aS pectase and thrombase; and (3) such as cause oxidation— 
that is, the oxidases. 
It was to be expected from analogy that enzyms of the first and third 
groups would occur in the tobacco plant, and, since the activity of the 
enzyms is not only of physiological value to this plant itself, but in this 
case is also of practical importance to the tobacco planter, it was impor- 
tant to prove their presence beyond a doubt. Two oxidizing enzyms 
have been shown by the writer to exist in the tobacco plant,’ and 
recently a third one has also been observed. This will be described 
further on. 
DIASTASE IN THE TOBACCO LEAF. 
The disappearance of starch in the early part of the curing process 
is due to the presence of diastase. It has been asserted that diastase 
does not occur in leaves and that protoplasm itself is capable of doing 
the same work.’ This appears very improbable, since both starch and 
protoplasm are insoluble in water. It is, however, somewhat difficult 
to demonstrate the presence of small quantities of diastase in the juice 
of leaves, since some can easily be retained by the pressed residue. 
Brown and Morris have observed that powdered leaves, if directly 
digested with some starch paste, gave a diastatic action of much greater 
intensity than was obtained when juice corresponding to that amount 
of leaf substance was applied. 
1This method is practiced extensively by Mr. G. Barnes, of Hatfield, Mass. 
2Report No. 59, U.S. Department of Agriculture. 
3’ Wortman observed that leaves killed with chloroform or kept in an atmosphere 
of carbonic acid show no decrease of starch, and hence inferred the absence of dias- 
tase in leaves; but this is not justified, for several reasons. Recently it has been 
Shown by A. F. Woods that diastase is easily changed by oxidizing enzyms. Fur- 
thermore, Vines, and also Jentys, have given new proofs of the presence of diastase 
in leaves. 
