Page:Popular Science Monthly Volume 68.djvu/62

58 the leaf sheaths enclosing the ear. It is just as possible for the lateral branches to develop pistillate flowers as for the central spike, and they often do so. The accompanying photograph (Fig. 2) exhibits a case in which we have the central spike and also the lateral branches developing pistillate flowers. But ordinarily in evolution when one portion begins to develop it is at the expense of other adjacent parts. In such case, the development of the central spike of the tassel is accompanied by the disappearance of the lateral branches. By removing the surrounding 'nubbins' we find that there is a normal ear in the center.

The central spike of the normal tassel usually has from four to eleven rows of spikelets in pairs, making eight to twenty-two rows of corn when developed, while the lateral branches usually have only two rows of spikelets in pairs, making only four rows of grain when well developed.

It is interesting to note the morphological changes which take place in the modification of the staminate flower into the pistillate. The staminate spikelets are borne in pairs (sometimes in threes), one sessile, the other pedicellate, the pairs alternating. As already stated, the pairs of spikelets are borne in two rows on the lateral branches, and in four to eleven rows on the central spike of the tassel (Fig. 3). The structure of the staminate spikelet is shown in Fig. 4. The outer glumes enclose two sessile flowers, and are 7-12-nerved; flowering glumes are 3-5-nerved, the palet 2-keeled, lodicules 2, fleshy and truncate. There is usually more or less difference between the upper and lower flowers in a spikelet; the upper flower matures first, and the palet is larger than the glume, while in the lower flower the glume is larger than the palet (Fig. 4).

The first tendency toward the development of a pistillate flower is indicated by a shortening of the pedicellate spikelet until it becomes