This section is from "Scientific American Supplement Volumes 275, 286, 288, 299, 303, 312, 315, 324, 344 and 358". Also available from Amazon: Scientific American Reference Book.
To be intelligible, I must commence by some very brief remarks on the tissues of vegetables. There are two sorts distinguished among plants; some seem of no importance in the phenomena of nutrition; others, on the contrary, tend to the assimilation of the organic or inorganic components which should nourish and develop all the parts of the plant. The latter have a striking analogy with ferments; their composition is almost similar, and their action is increased or diminished by the same causes.
These tissues, formed in a state of repose in vegetables as in grain, have special properties; thus the berry possesses a pericarp whose tissues should remain foreign to the phenomena of germination, and these tissues show no particularity worthy of remark, but the coating of the embryo, which should play an active part, possesses, on the contrary, properties that may be compared to those of ferments. With regard to these ferments, I must further remark that I have not been able, nor am I yet able, to express in formula my opinion of the nature of these bodies, but little known as yet; I have only made use of the language mostly employed, without wishing to touch on questions raised by the effects of the presence, and by the more complex effects of living bodies, which exercise analogous actions.
With these reservations I shall proceed to examine the tissues in the berry which help toward the germination.
THE EMBRYO (10, see woodcut) is composed of the root of the plant, with which we have nothing to do here. This root of the plant which is to grow is embedded in a mass of cells full of fatty bodies. These bodies present this remarkable particularity, that they contain among their elements sulphur and phosphorus. When you dehydrate by alcohol 100 grammes of the embryo of wheat, obtained by the same means as the membrane (a process indicated later on), this embryo, treated with ether, produces 20 grammes of oils composed elementarily of hydrogen, oxygen, carbon, azote, sulphur, and phosphorus. This analysis, made according to the means indicated by M. Fremy, shows that the fatty bodies of the embryo are composed like those of the germ of an egg, like those of the brain and of the nervous system of animals. It is necessary for us to stop an instant at this fact: in the first place, because it proves that vegetables are designed to form the phosphoric as well as the nitrogenous and ternary aliments, and finally, because it indicates how important it is to mix the embryo and its dependents with the bread in the most complete manner possible, seeing that a large portion of these phosphoric bodies always become decomposed during the baking.
This membrane (6), which is only an expansion of the embryo, surrounds the endosperm; it is composed of beautiful irregular cubic cells, diminishing according as they come nearer to the embryo. These cells are composed, first, of the insoluble cellular tissue; second, of phosphate of chalk and fatty phosphoric bodies; third, of soluble cerealine. In order to study the composition and the nature of this tissue, it must be completely isolated, and this result is obtained in the following manner.
The wheat should be damped with water containing 10 parts in 100 of alcoholized caustic soda; at the expiration of one hour the envelopes of the pericarp, and of the testa Nos. 2, 3, 4, 5, should be separated by friction in a coarse cloth, having been reduced by the action of the alkali to a pulpy state; each berry should then be opened separately to remove the portion of the envelope held in the fold of the crease, and then all the berries divided in two are put into three parts of water charged with one-hundredth of caustic potash. This liquid dissolves the gluten, divides the starch, and at the expiration of twenty-four hours the parts of the berries are kneaded between the fingers, collected in pure water, and washed until the water issues clear; these membranes with their embryos, which are often detached by this operation, are cast into water acidulated with one-hundredth of hydrochloric acid, and at the end of several hours they should be completely washed. The product obtained consists of beautiful white membranes, insoluble in alkalies and diluted acids, which show under the microscope beautiful cells joined in a tissue following the embryo, with which it has indeed a striking analogy in its properties and composition. This membrane, exhausted by the alcohol and ether, gives, by an elementary analysis, hydrogen, oxygen, carbon, and azote. Unfortunately, under the action of the tests this membrane has been killed, and it no longer possesses the special properties of active tissues. Among these properties three may be especially mentioned:
1st. Its resistance to water charged with a mineral salt, such as sea salt for instance
2d. Its action through its presence.
3d. Its action as a ferment.
The action of saltwater is explained as follows: When the berry is plunged into pure water it will be observed that the water penetrates in the course of a few hours to the very center of the endosperm, but if water charged or saturated with sea salt be used, it will be seen that the liquid immediately passes through the teguments Nos. 2, 3, 4, and 5, and stops abruptly before the embryo membrane No. 6, which will remain quite dry and brittle for several days, the berry remaining all the time in the water. Should the water penetrate further after several days, it can be ascertained that the entrance was gained through the part No 10 free of this tissue, and this notwithstanding the cells are full of fatty bodies. This membrane alone produces this action, for if the coatings Nos. 2, 3, 4, and 5 be removed, the resistance to the liquid remains the same, while if the whole, or a portion of it, be divided, either by friction between two millstones or by simple incisions, the liquid penetrates the berry within a few hours. This property is analogous to that of the radicules of roots, which take up the bodies most suitable for the nourishment of the plant. It proves, besides, that this membrane, like all those endowed with life, does not obey more the ordinary laws of permeability than those of chemical affinity, and this property can be turned to advantage in the preservation of grain in decortication and grinding.