Lignin and Cellulose 
The outstanding result of this work is the uniformly high 
yield of lignin in springwood as compared with that in summerwood, 
showing that the wood substance laid down in the early growing season 
differs chemically from that grown in the late growing season. The 
high proportion of lignin to total constituents in the springwood is 
accompanied by a low percentage of cellulose except in the heartwood 
of loblolly pine and of red alder, in which the percentage of cellu- 
lose is also slightly higher in the springwood. Even here, however, 
the ratio of lignin to cellulose is higher in the springwood than in 
the summerwood. 
An explanation of why the lignin constitutes a larger per- 
cent of the total wood substance in springwood than in summerwood is 
already available in a recent paperl by Hitter in which it was shown 
that the lignin is located partly in the cell wall mixed with the cel- 
lulose and partly in the middle lamella v/ith very little, if any, other 
substance present. If the ratio of lignin to cellulose in the cell 
wall, exclusive of the middle lamella, is the same in springwood as 
in summerwcod, then the lignin in the middle lamella, which constitutes 
a greater proportion of the total wood substance in the springwood, 
would account for the higher proportion of lignin in springwood than 
in summerwood. 
The remaining determinations showed no uniform differences 
in chemical composition between springwood and summerp/ood, although a 
tendency was apparent toward higher percentages of (a) pentosans in 
the springwood; (b) pentosans in the isolated springwood cellulose; 
(c) extractives in the springwood. 
Conclusions 
Th<=. data of this paper indicate that: (l) A higher 
percentage of lignin exists in springwood than in summerwood. An 
explanation is offered for the different lignin yields in the tv/o 
bands of growth. 
(2) Cellulose forms a larger percentage of the total wood 
substance in summerwood than in springwood. 
industi 
:rial & Engineering Chemistry, 17:119^ (1925), 
R950 -2- 
