+-----------------+---------+-----------------+-----------+---------+---------+
|Stems and Foliage|Per cent | Fodder Crops. |Per cent of| Cereal |Per cent |
| of Root Crops. |of Fibre.| | Fibre.* | Straws. |of Fibre.|
+-----------------+---------+-----------------+-----------+---------+---------+
| White Turnip | 3.9 | Grasses | 32.0 | Oats | 60.68 |
| Swedish Turnip | 4.2 | Meadow Hay | 25.8 | Wheat | 75.77 |
| Carrot | 3.1 | Clover & Trefoil| 23.5 | Barley | 71.74 |
| Mangel | 2.6 | Vetches | 25.9 | | |
| Parsnip | 2.6 | Lucerne | 26.7 | | |
| | | Sainfoin | 28.7 | | |
+-----------------+---------+-----------------+-----------+---------+---------+
+------------------+-----------+-----------+-----------+-----------+----------+
| | | | Stems and | Fodder | Cereal |
| |Leguminous.| Oil Seeds.|Foliage of | Crops. | Straws. |
| | | |Root Crops.| | |
+------------------+-----------+-----------+-----------+-----------+----------+
|Average % of water| 14 | 7 | 87 | 70-80 | 15 |
+------------------+-----------+-----------+-----------+-----------+----------+
* This percentage is calculated on airdry-produce containing 15% of
water.
The above figures have a purely empirical value, since they represent a
complicated mixture of various residues derived from the celluloses and
compound celluloses. This mixture may be further resolved, and by
special quantitative methods the proportions of actual cellulose,
ligno-cellulose and cuto-celluloses estimated (J. Konig, _Ber._, 1906,
39, p. 3564). The figures are taken as an inverse measure of
digestibility; at the same time it has been established that this group
of relatively indigestible food constituents are more or less digestible
and assimilable as flesh and fat producers. The percentage or
coefficient of digestibility of the celluloses of the more important
food-stuffs--green fodder, hay, straw and grains--varies from 20 to 75%.
It has also been established that their physiological efficiency is,
under certain conditions, quite equal to that of starch.
It must also be borne in mind that the indigestible food residues, as
finally voided by the animal, have played an important mechanical part
as an aid to digestion of those constituents more readily attacked in
the digestive tract of animals. They are further an important factor of
the agricultural cycle. Returned to the soil as "farm-yard manure,"
mixed with other cellulosic matter which has served as litter, they add
"fibre" to the soil and, as a mechanical diluent of the mineral soil
components, maintain this in a more open condition, penetrable by the
atmospheric gases, and promoting distribution of moisture. Further by
breaking down, with production of "humus," a complex of colloidal
"unsaturated" bodies of acid function, they fulfil important chemical
functions by interaction with the mineral soil constituents.
_Chemistry of Cellulose._--Purified cotton cellulose, which is the
definitive prototype of the cellulose group or series, is a complex of
monoses or their "residues." It is resolved by solution in sulphuric
acid and subsequent hydrolysis of the esters thus produced into
dextrose. This fundamental fact with its elementary composition, most
simply expressed by the formula C6H10O5, has caused it to be regarded as
a polyanhydride of dextrose. Forming, as it does, simple esters in the
ratio of the reacting hydroxyls 3OH: C6H10O5, and taking into account
its direct converson into [omega]-brom-methyl furfural (Fenton) a
constitutional formula has been proposed by A.G. Green (_Zeit. Farb.
Textil Chem._ 3, pp. 97 and 309 (1904)), which is a useful
generalization of its reactions, and its ultimate relations to the
simpler carbohydrates, viz.,
CH(OH).CH.CH(OH)
| >O >O
CH(OH).CH.CH2 .
Green considers, moreover, that a group thus formulated may consistently
represent the actual dimensions of the reacting unit, but that unit of
larger dimensions, if postulated, is easily derived from the above by
oxygen linkings.