240 ILLINOIS STATE HORTICULTURAL SOCIETV. 



ammonia ; that this ammonia passes into plants, and furnishes them the nitrogen essen- 

 tial to growth. Not to mention the many and grave objections to this view, based on 

 fact, as well as on theory, it may be said we have in the simple drying of gypsum, 

 mixed or unmixed with soil, a source of nitrogen in the form of nitrous acid, and that, 

 too, without the intervention of ammonia, which will go far in explaining the beneficial 

 effect of this substance on oils. 



Those who have studied the assimilation of nitrogen by plants, have generally 

 traced its origin to ammonia, probably because ammonia salts, particularly the carbonate, 

 exert so favorable an influence on vegetable growth. But there seems to be no known 

 reason, why nitrogen may not enter a plant and become assimilated equally well in the 

 form of nitrous or nitric acid, as of ammonia. Indeed, it is well known that nitrates, as, 

 for instance. Chili, and particularly common saltpeter, are excellent fertilizers. These 

 are regarded by Mr. Lawes, of the famous farm at Rothamsted, as among the very best 

 means or increasing the productive power of soils ; and this beneficial effect is doubtless 

 due in large measure to the nitrogen in the salt. Now if nitrogen in the form of nitrous, 

 or of nitric acid can enter a plant and become assimilated, and if, moreover, the simple 

 drying of gypsum induces the formation of these acids in soils, it is easy to see at least 

 one relation that gypsum may sustain to plant life. That this is the only agency of gyp- 

 sum in vegetable growth is by no means asserted ; but experiment teaches that this is at 

 least one way in which it may act beneficially. 



It may be added, that in so far as gypsum improves a soil by supplying nitrous acid, 

 pulverized marble, or common limestone, would seem to be equally valuable, or better, 

 since experiment teaches that a larger quantity of nitrous acid is formed by the drying 

 of marble, than by the drying of gypsum ; and this suggests whether the addition of 

 ground limestone would not be equally beneficial to a soil. In fact, this may be, in 

 part the true explanation of the beneficial effect of marl and chalk, and shell sand, 

 which are applied in large quantities to soils in different parts of England, Scot- 

 land, Ireland and France. The benefit has generally been ascribed to the lime fur- 

 nished to the plants with some organic and other matter usually present in these sub- 

 stances. So far as appears, they have never been regarded as a source of nitrogen to 

 plants. 



But if nitrous acid is formed by the simple drying of a soil containing an alkaline 

 carbonate, at a moderate temperature, the natural suspicion would be that this acid would 

 be found in the juices of plants. As soon, therefore, as we had become convinced of 

 the truth of the statements of Jeannel by repeating his experiments, we proceeded to 

 examine plants for nitrous acid. We sought it in the root, in the stem, and in the leaf. 

 We sought it in a large variety of plants, and in the spring during vigorous growth. 

 In many it was found in abundance; in others, only a small quantity, while in others, 

 not a trace could be detected. Generally, it may be said, that just at the top of a plant, 

 where the young leaves are unfolding, and where the stock is in process of elongation, 

 will nitrous acid be found, if found at all. There it was found in the stalk of the potato, 

 although in small quantity. In other plants, like the common garden lettuce, the whole 

 leaf seems to be saturated with it. Here may be mentioned the common garden rhubarb, 

 [)-heum rhaponticum), the dandelion, (taraxacum densleonis), the common plantain, 

 [plantago major), shepherd's purse, {capsclla bursa pastoris), and the May apple [podo- 

 phylhim pcllatiim). Clover gave feeble signs of nitrous acid, while in general the 

 grasses showed very slight, if any indications of it. Some plants not only gave no per- 

 manent indications of nitrous acid, but seemed to contain some reducing agent by which 

 the acid, as soon as present, was immediately destroyed. Possibly in such cases, the 

 acid was in the act of having its nitrogen assimilated by the plant, and, therefore, failed 

 to give any signs of existence. The juice of young stalks of corn, two or three inche- 

 high, crushed in a mortar with a little pure water and filtered, not only gave no 

 indications of nitrous acid, but instantly destroyed the indications of some that was 

 added. Some substance of a reducing nature, therefore, is evidently present in the corn, 

 which not only destroys the nitrous acid that may enter through the roots, but destroys 

 that even which is added. The same is true also of the roots of corn, and also of the 

 young stalks and roots of wheat and rye ; and the same is prolwbly true of oats and 

 barley, although experiments have not been made with them, except with barley that 



