greater relative quantity of roots in the ripe clover plant. You have half as much roots as top, in the clover plant, whereas you have almost fourteen times as much top as roots in the ripe rye plant. These plants, then, are very different in the way in which they act upon the soil, and therefore in the way in which they leave the soil. When you reap rye close to the ground you take away one hundred and thirty-six out of one hundred and forty-six pounds, and thus leave very little in the soil. When you cut clover you may leave half as much in the ground as you take off. That is a point of great importance in considering their relative bearing upon the question of exhaustion, and shows that yon may expect a very different result from leaving clover roots and clover stubble in the soil than from the roots and stubble of rye.

MR. LYMAN. If we cut the rye low we take very nearly the whole of the plant off from the land, and it requires five times as much put back to bring the rye field up to an equality with the clover field, as it stands cut, with the roots in the ground. Therefore we cannot look for a crop that would be equal to what clover would bring us unless we restore this ratio.

PROF. JOHNSON. You are right.

MR. LYMAN. What is the difference if we plow the two crops under.

PROF. JOHNSON. The total weight of your rye crop is 272; the total weight of clover is 246; so that in this case the clover has a somewhat less absolute mass of vegetable matter.

QUESTION. There are two or three other important questions. We want to know if the plants take from the soil a certain amount of manurial constituents or saline matter?

PROF. JOHNSON. They do, of course. That is one of the first principles of agriculture.

QUESTION. Do these roots left in the soil create any thing? PROF. JOHNSON. Nothing whatever.

QUESTION. Then they take from the soil manures to grow them, the same as what you take off?

PROF. JOHNSON. Certainly. They take manures or equivalent nutritive matters.

QUESTION. It took all these manurial matters to make this crop, and if you carry it off you carry off those manurial matters; whatever you leave restores what it took to make it, and no more?

MR. GOULD. Ought it not to be said that in its previous condition the manurial matter was in an insoluble condition, not adapted to the plant; whereas, what you leave is in a soluble condition, and assimilable?

PROF. JOHNSON. During the growth of a crop, plant-food in the soil does pass from an insoluble into a soluble form, and being taken up by the crop remains in that part of the crop left in the field in a state adapted for immediate use. The deep-rooted clover also, in this case, brings up, from an average depth of sixteen inches, matter which remains in part within the range of shorter-rooted grain crops.

SECOND LECTURE.

PROF. JOHNSON. I was speaking yesterday on the peculiarities of plants which enable them to act differently on the stores of nutriment which may be supplied to them in the soil. I spoke of the differences in the absolute quantity of roots which various plants put out into the soil, and also of the differences in the depths of roots; and gave some illustrations on those points. I propose to speak this morning of the different structure of the foliage of plants.

We know with absolute certainty that a large share of the feeding of the plant is done through the leaves. We cannot certainly tell how much goes on through the leaves and how much through the roots, in highly manured and very rich soil, but experiments have demonstrated that all the carbon of the

plant (which is about fifty per cent of the weight of the dry plant) may come from the atmosphere; it is not necessary that any of it should come from the soil. The seeds of various agricultural plants-Indian corn, oats, barley, etc.-have yielded a larger increase under artificial circumstances, where the roots had no carbon whatever at their disposal, than is ever produced under field culture. It is a well-known fact of agricultural practice, that soils which are nearly destitute of vegetable matter, and therefore have no considerable source of carbon in them, will produce large crops. Some very sandy soils, containing but little carbon, may be made to produce heavy crops by irrigation. Crops are also raised on soils free from organic matter, or from sources of carbon, by the aid of fertilizers which themselves furnish nothing of that sort.

Carbon, then, which makes up half of the weight of the dry plant, is always chiefly supplied by the atmosphere and may be supplied by the atmosphere exclusively. It is not necessary that it should be in the soil. The nitrogen of the plant, which forms indeed a small proportion-two per cent. perhaps, as an average of the dry plant, is still an important ingredient, for without it vegetation cannot exist.

Some crops have the power of gathering nitrogen without any difficulty; they not only supply themselves with it, but they even cause its accumulation in the soil. There are other crops which are dependent upon artificial supplies of nitrogen, unless the soil be naturally very rich in this elementcrops which, if we undertake to raise them continuously on the same field, presently begin to show that they lack something, while if we apply nitrogenous compounds as fertilizers, the growth is ensured. We do not know in full detail how plants acquire a sufficient supply of nitrogen from the atmosphere, but we conclude, with great probability, from the results of practice, that different plants draw on the natural supplies of nitrogen in a different way.

Let us consider how the structure and habits of two typical

crops, wheat and clover, stand in relation to their power of assimilating atmospheric nourishment. In respect of foliage we cannot certainly say that the wheat plant or the wheat crop when full grown exposes a less surface to the air than full grown clover, but we know that the leaves of wheat, as of all our cereals, maintain their green color and succulence during a much shorter time than is true of clover. In case of winter grain the period of leaf-activity usually begins in October and ends shortly after heading out, in June, some weeks before the crop is harvested. Clover, on the other hand, is not arrested in its growth by any crisis of seed-production, but, when cut for hay, sends up new shoots, unfolds new leaves, and shortly yields an aftermath, its growth going on uninterruptedly all the summer and late into autumn, until checked by heavy frosts.

That the actual leaf surface of the clover crop, taking its duration into account, is much greater than that of the wheat crop, I do not doubt, because although the total weight of the harvested crops is, on the average, not very unlike when clover is cut for hay, the total amount of vegetable matter organized is much greater in case of clover than in that of wheat, as appears from the table on page 215, where clover roots are seen to constitute two-fifths (equal to six-fifteenths) of the entire plant, while the roots of rye, which doubtless do not differ much from those of wheat, are but one-fifteenth of the entire plant.

You see that the foliage and mode of life of these two classes of plants are very different for the purposes of gathering food from the atmosphere, and they must therefore be expected to leave the soil in very different condition, because their roots remain there, and the material of those roots is

gathered very largely from the atmosphere; so that when we raise a grain crop we leave in the soil a small quantity of material taken from the air, but when we cultivate a deeprooted plant which grows the season through, we leave a large amount of atmospheric matter in the soil.

Again, in ordinary culture some plants are permitted and required to reach a crisis of growth which others are not allowed to attain. This crisis is seed-production.

Our meadow grasses are of the same botanical order as the cereal grains; which means that all these plants are of the same great race and closely resemble each other in their most characteristic features. The noble wheat and the scoundrel quack are, in fact, brothers of the same family, both being of the genus Triticum. The latter is sometimes termed wheatgrass, as if in allusion to this brotherhood. There are two other grasses, vagabond members of the wheat family, living obscurely in this country. Barley and the oat have each two brothers of low degree-worthless grasses, living on salt or sandy shores, or on rocky hills, and unknown to the cultivator.

If wheat, instead of being allowed to ripen its seed, as is our universal practice, should be mown or fed off just before heading out, it would throw out new shoots and continue to grow the summer and autumn through, would come on the second year and deport itself as a perennial; would in fact, become grass in the usual sense of that word.* Wheat is probably not hardy enough to make a good substitute for Timothy, but it is sufficiently so to justify our statement.

The reason why wheat under our culture is an annual is that the process of seeding exhausts the plant, and as a consequence it dies out naturally. It is the universal opinion among farmers that the meadow grasses are weakened very

*In the year 1858, a frost fell upon the wheat fields in the central portions of this State just as the wheat was in blossom, and such wheat fields were ruined so far as the production of grain was concerned. The farmers declared that "wheat in blossom was as tender of frost as the tomato." Some of the farmers mowed these wheat fields for fodder, and were greatly astonished to find that the wheat stubble again sprouted and made a vigorous second growth. Unfortunately it was plowed in the fall and not suffered to produce a wheat crop the succeeding year. K.