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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.1 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.2
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. Bui. 5 (1889).
* Mich. Bui. 154 (1898), p. 272.
is shaded, and, consequently, a less number of stalks can be raised per acre.
In some localities the ear may be too high on the stalk to be husked easily. While there are wide variations due to variety, soil, climate and thickness of planting, the weight of field-cured
stover has been estimated at about one and one-third pounds for each pound of grain produced. In actual dry matter the yield per acre may be estimated as about equal under ordinary field culture. It has been estimated that for every pound of dry matter produced in the roots and stub ble when cut close to the ground, six pounds are produced in the plant above ground.1
214. The Inflorescence.—The cultivated maize plant bears its carpels and stamens in separate flowers. The staminate flowers borne in a panicle of spikelets at the top of the culm are called The carpellate flowers are borne in the
Dent maize, variety Sibley's Pride of the North. Compare with flint variety upon opposite page. Note that this variety has no suckers and that the husks have completely tost their leaf blades. Plant has been In tassel about two weeks. It is not as mature as the flint variety, hence the ear is relatively small. (One twentyfourth natural size.)
collectively the tassel.
I Wis. Rpt . 1892, p. 119. In this connection, see also Mo. Bui. 9.
axils of the leaves, forming upon maturity what is known as the ear. The fruit of the maize plant being borne in the axils of the leaves rather than being terminal is a feature which distinguishes maize from all the other cereals. The difference is more apparent than real. Certain varieties of maize, especially pod maize, sometimes bear carpels upon the tassel of the main culm, and where branches occur bear both stamens and carpels at their end.
It is assumed that wild maize was a branched plant containing perfect flowers (both carpels and stamens) on the terminal tassel and, also, at the end of the branches. Since the plant is wind fertilized and the pollen tends to fall, the carpellate flowers in the terminal tassel would be less perfectly pollenized than those on the branches below. The pollen on the branches would tend to fall to the ground, thus being of little value. The plants which had the greatest development of carpels on the branches and of stamens in the terminal tassel would tend to survive. As the end of a branch became laden with a collection of grains (ear) the short branch would
Flint maize, variety Smut Nose. Compare with dent variety upon opposite page. Note two good ears with rudimentary one below upon main culm, and also the leaf blades upon the husks of the ear. The other three culms are suckers, all having grown from one seed. Plant has been in tassel about three weeks. (One-twenty-fourth natural size.)
best hold the ear from drooping. Thus the culm of the branch (now called the shank) has become a succession of nodes with short internodes. Each node still bears the sheath of the leaf, the blade being much reduced in size or aborted. This collection of leaf sheaths is called the husk. The branch has been telescoped. (211.)
215. The Tassel.—The tassel is a spreading panicle generally a foot or more in length in field varieties, with branches usually six to ten inches long. The spikelets extending from base to tip of each branch (rachis) are arranged in clusters of two to four, one usually pediceled, the others sessile, or all sessile, the clusters often overlapping. The empty or outer glumes, about equal, three-eighths to one-half inch long, are stouter and harder than the flowering glume and palea. The latter are about equal and shorter than the outer glumes. They are hyaline and much thinner. Each flower bears three stamens. The anthers are large, nearly as long as the flowering glume. They are attached to the filament on one side near the lower end.
Lazenby estimates that 45,000 pollen grains are produced for each ovule in dent maize.1 According to another estimate, an average maize plant has seventy-two hundred stamens, containing about eighteen million pollen grains. Assuming two thousand ovules to a plant, there would be nine thousand pollen grains to an ovule.2 It is held that the staminate flowers usually mature before the carpellate, but they may mature at the same time or later.
216. The Silk.—The style, commonly known as the silk, arises at the summit of the carpel. In certain varieties, as pop maize, the scar may be plainly seen on the top of the ripened grain. Since the end of all silks, for the silk to be effective, must protrude beyond the surrounding husk, the silk may be a
» Proa Soc. Prom. Agr. Sc. (1898). » Sargent: Corn Plants, p. 44.
foot or more in length. Near the base of the silk on the side opposite the embryo there is an opening through the wall of the ovulary to which has been given the name stylar canal. It is not known positively whether the pollen tube passes down through the substance of the silk, entering the ovulary by way of the base of the silk, or whether the pollen tube enters the ovulary through the stylar canal. Guignard and others believe the latter to be the case.12 Whether the pollen tube before entering the stylar canal grows down the outside of the silk or whether the pollen grain by some mechanical means reaches the opening to the stylar canal is likewise unknown. After pollination, the silk dries up but persists. When, however, pollination is prevented, the silk grows to unusual size and remains green two or three times as long as normal.
217. The Ear.—The ear may vary from one-half an inch to sixteen inches long and may have from four to forty-eight rows in individual ears. A variation of from four to twelve inches in length and from eight to twenty-four rows is not uncommon and may obtain as a variety characteristic.
The ear may be looked upon as being formed by the growing together of four or more spikes, each joint of the rachis bearing two spikelets. Each spikelet is two-flowered, the lower one being abortive (214); thus the distinctly paired rows often observed represent a pair of spikelets. The growing together
I Guignard, L.: La double fecondation dans le mais. Jour. d. Bot . 15: 1-14 No. 2, 1901.
a Poindexter, C. C: The Development of the Spikelet and Grain of Corn Ohio Naturalist, Vol. IV, No. 1, Nov. 1903.
A spikelet of maize before fertilization ; s, style or silk ; c, the stylar canal through which, perhaps, the pollen tube enters the ovulary; I, inner glume; o, outer glume. Enlarged twelve times (after Poindexter).