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for fodder purposes, and gama grass (Tripsacum dactyloides L.) which was a rather conspicuous feature of the native herbage of the prairie regions in the central and southern portions of the United States.
The wild prototype of Zea has not with certainty been identified. So far as known there is only the one species which includes all the cultivated types and varieties of maize.?
209. Roots.—The form and habit of growth of the roots of maize are similar to those of wheat, although modified somewhat in position, due doubtless to the plant being in hills or drills instead of being broadcast. The general tendency is for the roots to grow somewhat horizontally for one or two feet and then turn down more or less abruptly. The position of the roots is modified by the depth of fertile soil and by depth to which the seed bed has been stirred. The indications are that the distribution of roots depends more upon a proper supply of oxygen and water than upon temperature. The following table shows a Brace roots on Mex.
ican maize grown number of roots at six inches from the plant at at lowa Station different depths in plants one to six weeks old as farm (after King). examined in a black prairie soil at the Illinois Station:
i For a summary of the evidence concerning the wild prototype of maize, see Maize: A Botanical and Economic Study. By John W. Harshberger. Contributions from the Botanical Laboratory of the University of Pennsylvania, Vol. 1, No. 2
* N. Y. State (Geneva) Rpt. 1887, p. 95: 1888, p. 171.
Observations made in Alabama, New York, North Dakota, Iowa and elsewhere, have shown that the roots grow horizontally for some distance from the plant, within four inches of the surface. These lateral roots are very abundant, especially in the early part of the season. Later in the season, however, roots are sent downward in greater number, the lateral roots meanwhile continuing to grow and rebranch, so that in the course of eight to ten weeks the soil between the hills, under ordinary culture, is completely occupied by a dense ramification of roots. One hundred branches have been counted on a piece of maize root fourteen inches long. Many instances have been reported of roots growing four feet deep, and in some cases roots have been broken off at a depth of fifty inches, showing that they must have grown somewhat deeper. Hays reports maize roots eight feet in length, although not in depth. In most soils, however, the amount of root surface below the first two feet is comparatively small. This suggests that the relatively few unbranched roots which descend to greater depth do so to supply the plant with water. The requirements of the plant for water are very great, both because of the large amount of dry matter per acre produced and because the season of active growth is during the hottest portion of the year.
In the early stages of the plant the root growth is rapid. A maize plant one-half inch high has been observed with a root eight inches long; one three inches high with a root thirteen inches long, and two five inches high with roots eleven to twentyfour inches long. Unlike the wheat plant, which throws out a whorl of three temporary or seminal roots, the radicle of the maize plant enlarges and remains prominent, while two or three other roots of lesser size are thrown out. Compared with the lower portion, the stem is very much enlarged at the point where the permanent or coronal roots begin. In a plant thirty days old and twenty-one inches high the stem between the temporary and permanent roots was one-sixteenth of an inch in diameter, while just above the permanent roots it was three-eighths by fiveeighths inch. The majority of the permanent roots begin at about one inch below the surface of the soil, regardless of the depth of planting. Brace roots, however, usually start from the node, one or two inches above ground. The aerial portion is much enlarged, but soon after entering the ground becomes reduced to the size of the other roots. A maize plant forty-three days old and five feet high was found to possess thirty-five roots, eleven of which were brace roots. None of the brace roots had entered the ground more than one and one-half inches. Their total length varied from one and one-half to five inches. An examination of the mature plants shows the brace roots to have grown to considerable depths, thus performing the function of true roots. Variety differences in ability to support the culm and prevent its being blown down have been observed, but this character has not as yet been made of practical value.?
210. Culms.—The maize plant is the most variable in size of the cereals. The height is reported to vary from eighteen inches in the Tom Thumb pop to thirty feet or more in the West Indies. Individual stalks twenty-two and one-fourth feet high have been reported from Tennessee. From four to twelve feet is a common variation. The height varies not only with the variety but the same variety varies largely with soil and climatic conditions. Along the Mississippi River, south of the fortieth parallel, it is not unusual to see maize growing on which the ears are so high that a man of ordinary height can barely reach them. In the northern latitudes of the United States, as in New England, much maize is so short as to make it necessary to stoop to reach the ears. The circumference of an average maize culm, between the first and second nodes, in a dent or flint variety, will be from three to four and one-half inches. Unlike most of the plants of the grass family, the culm of maize is not hollow, the interior being filled with a soft pith, which does not add mate rially to its strength. The internodes are alternately furrowed on the side next the leaf blade and on the side where the branch or ear may occur. In fact, furrows appear to occur for the accommodation of the branch or ear buds.
1 Miss. Bul. 33, p. 73.
The maize plant does not depend alone upon the node for erecting bent culms as in the other cereals and grasses generally, but the walls of the lower internode have a similar power. (378)
The per cent of crude fiber is considerably higher in the outside of the culm than in the pith, thus increasing the per cent of other constituents in the latter. Aside from this, the per cent of ash is higher in the pith, being especially high in potassium and calcium, while the culm wall is notably high in silica.
At the New York Station the rate of growth ranged from three to eighteen and one-half inches per week. Under specially favorable conditions a growth of five inches was recorded in one day. At the Illinois Station an increase in one week equal to 1,300 pounds of dry matter per acre was observed.
211. Suckers.—Under conditions of ordinary culture, one seed produces but one culm. When, however, the planting is not sufficiently thick for the existing conditions, the plant may produce one or more branches from its lower nodes, which branches will throw out separate roots. The branches or culms are known as suckers, and usually do not produce ears. They are not desirable because they take plant food and water from the soil without giving any return in grain. Some varieties of maize produce a number of branches from nodes higher up the culm. Ordinarily, however, the maize plant is unbranched except where its one or more ears are produced, the ear being produced at the end of a much modified branch. (214)
212. Leaves.-With dent maize grown in Iowa, the number of leaves on a culm varied from twelve to eighteen. Since the
1 C. S. Plumb: Indian Corn Culture, p. 14. a lowa Bul 2 (1888).
rface ma Plants pers found 1
lower leaves die off before maturity, activity at any one time is confined to about twelve. The width of the blade varied from three and three-quarters to five and one-eighth inches. At the Missouri Station the total external leaf surface on twelve living leaves of a single maize plant was found to be twenty-four square feet.? As 12,000 plants per acre are not an unusual stand, the leaf surface may be more than a quarter of a million square feet on an acre, or about six times the area on which the plant stands.
At the Michigan Station the leaves constituted somewhat more than a third of the dry matter when the grains were in milk, and a little more than a fifth when the plant was ripe. During this period the percentage of dry matter of culm remained about the same, the decrease in percentage of dry matter in leaves having been offset by a corresponding increase in the ears.
The outer edges of the leaf blade grow faster than the portion next the midrib, giving a wavy effect to the blade and giving it an elasticity which aids it to withstand wind. In the upper portion of the blade, on either side of the midrib, are to be found large wedge-shaped (bulbiform) cells which on filling with water cause the young leaf to unfold and which during drouth cause the leaf to roll, thus reducing the evaporation from the plant. The under surface of the leaf is further protected, also, against transpiration by a strong cuticle. The ligule tightly clasps the stalk, preventing the entrance of water and accompanying dirt between sheath and culm: it also prevents the sheath from rotating upon the culm as in most of the grasses.
213. Relationship of Grain to Stover. Of two stalks bearing the same quantity of grain, the smaller is to be preferred, where grain is the principal object sought. The larger the stalks the more food material necessary to produce them, the more ground
1 Mo. Bul. 5 (1889). & Mich. Bul 154 (1898), p. 272.