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Journal of Agricultural Research 
Vol. XXVII, No. s 
THE CHEMISTRY OF FIBROUS MATERIALS 
The amount of work which has been done on the chemistry of plant 
fibers is nothing short of monumental, and yet, despite the vast ac¬ 
cumulation of information now available, the chemistry of cellulose and 
of its combinations with pentosans, lignin, and allied substances in 
woody fiber is but imperfectly understood. Investigators are still at 
variance over the structure of the cellulose and the lignin molecule. 
The writer has made no attempt to review all or even any consider¬ 
able portion of the literature on the subject. A great deal of it is of a 
highly technical nature and of importance to the paper industry rather 
than to agriculture. It will be sufficient to outline the general concept 
of the chemistry of fiber as it exists at the present time, with such refer¬ 
ences as may be necessary. 
Plant fibers are simply an aggregation of the cell walls of certain 
specialized cells occurring in the plant. These cell walls become elabo¬ 
rated, enlarged, and strengthened with age until maturity is reached, at 
which time, in high-fiber plants at least, they constitute the major por¬ 
tion of the individual cells and of the vegetative portion of the plant, 
the protoplasm having been almost, if not altogether, absorbed, or trans¬ 
ported to the seed. 
In the early stages of growth the cell wall is known to consist of prac¬ 
tically pure cellulose, but with advancing age it becomes changed to a 
compound cellulose known as ligno-cellulose, which is characteristic of all 
fibrous or woody material and which imparts to such substances their 
property of rigidity. The process by which the cellulose is converted 
into ligno-cellulose is known as lignification. Just what this process in¬ 
volves in the way of chemical change and how it proceeds are still mat¬ 
ters of dispute. Some investigators are of the opinion that it is purely a 
physical phenomenon; that the cellulose is simply embedded in, or in- 
crusted by, the lignin; while others hold that the two are chemically com¬ 
bined and that the ligno-cellulose is formed at the expense of the cel¬ 
lulose. 
Magnus (jo, p. 12) considers that a definite linkage exists between the 
cellulose and the lignin. 
Casparis (7) in a paper published in 1920 concludes that “lignified cell 
walls do not consist of chemically homogeneous material’’ and that “it 
appears likely that intramolecular formation of lignin takes place from 
the carbohydrates originally present in the cell wall.” 
Rassow and Zschenderlein (34) have evidence which points toward the 
pentosans as intermediate products in the formation of lignin. 
Perhaps the most recent view of the process of lignification is that set 
forth by Esselen ( 12 ). He says in part: 
It has been demonstrated that lignin is made up of hydrosols of high molecular 
weight which are absorbed from the sap by the cellulose fibers. . . . The maximum 
lignification coincides with the maximum percentage of absorbable colloidal sub¬ 
stances in the sap. While the lignification depends mainly on the absorption referred 
to, it may be followed by certain chemical reactions, particularly dehydration, 'which 
manifest themselves in toughening and ageing. 
In whatever way the transformation is brought about, the final prod¬ 
uct is the highly complex ligno-cellulose, the ultimate structure of which 
still baffles the chemist. It is, however, generally agreed that the com¬ 
plex consists of cellulose linked in some way with two noncellulose sub¬ 
stances, one of which contains an aromatic nucleus, while the other, be- 
