STUDIES ON THE CURING OF LEAF TOBACCO. 3 



looked the importance of translocation when the leaf is cured on the 

 stalk. 



It is, of course, well known that during the growth and development 

 of the plant there is a movement of the products of photosynthesis, 

 rendered soluble by enzyms when necessary, from the more mature 

 leaf through the stalk to the younger growing parts. Essentially 

 the same thing takes place after the cut plant has been placed in the 

 barn, except that the materials transported are derived wholly from 

 the surplus food supply of the leaf. While the leaf web perishes in a 

 few days, the midrib remains alive for longer periods and the stalk 

 may remain perfectly green for several weeks. Secondary shoots, or 

 suckers, developing in the leaf axils, may be found growing at the 

 end of several weeks, and the necessary food supply for the stalk and 

 the suckers is derived from the leaf surplus. An interesting con- 

 firmation of this phenomenon is found in the case of excessive mois- 

 ture prevailing in the barn during the later stages of curing, a condition 

 which leads to the decay of the leaf known as pole-sweat. The 

 excessive moisture causes the dying leaf cells to retain more water, 

 thus facilitating the more complete translocation of food materials 

 into the stalk. Under these circumstances the so-called absciss- 

 layer is formed at the juncture of the midrib with the stalk, so that 

 the leaf is cast off as a useless appendage. Under normal curing 

 conditions the leaves remain firmly attached to the stalk. 



LOSS IN WEIGHT OF DRY MATTER IN AIR CURING WHEN THE LEAF 



IS PRIMED. 



The first problem met with in a physiological study of curing is the 

 total loss in dry weight which occurs in the process. So far as we 

 know, no accurate determinations have been previously made on this 

 point, at least in this country. Because of the important r61e of 

 translocation in curing, the loss in weight depends largely on the 

 method used in harvesting the tobacco. So far as it relates to loss in 

 weight of the whole leaf, translocation can play no part when the 

 leaf is separated from the stalk in harvesting. 



Our experiments cover the crop years of 1908 to 1911, inclusive, a 

 period of four years, and were confined to the cigar-wrapper-leaf 

 section of Connecticut, the experimental material all being obtained 

 from the farm of W. S. Pinney, Sufneld, Conn. The types of tobacco 

 included in the experiments are the Havana Seed, the Halladay, and 

 a so-called John Williams broadleaf . The Havana seed is one of the 

 old standard types of domestic cigar-wrapper leaf and the Halladay 

 is a new type developed from a cross of Havana seed on Sumatra. 

 The history of the John Williams type of broadleaf is not known, but 

 it differs decidedly from the ordinary broadleaf, and its habits of 

 growth strongly suggest its origin from a cross of the latter on Cuban. 



