DEVELOPMENT OF EAR 



49 



tains 7,500 pollen sacs, making a total of 20,250,000 pollen grains per 

 plant in the corn field. This excess of pollen is necessary because of 



the loss of so many grains which are 

 lodged about the stalk and which fall to 

 the ground. If every grain were to reach 

 a silk there would be 20,250 grains for 

 each ovary, if each stalk produced but 

 one ear, or 10,125 m case of two ears, 

 counting i,ooo ovaries per car. 



FEMALE OR PISTILLATE FLOW- 

 ERS. The female flowers are borne on a 

 hardened spike (cob), which is produced 

 on a branch or shank coming from a node 

 on the main stem. At first, the leaf sheath 

 covers and protects this outgrowth, but 

 it soon appears above the sheath and the 

 corn is said to be "shooting." In a short 

 time, the husks, which are modified leaves, 

 open at the tip end and silks appear. The 

 outer end of each silk, a portion of the 

 stigma, is often split, and is covered with 

 ^'e^Y short hairs which, together with a 

 sticky or mucilaginous secretion present, 

 aid in cnllecting pollen grains. 



The remainder of the silk to its attach- 

 ment is the style, which is slightly angu- 

 lar and is tubular. The style is attached 

 to the summit of the ovary (kernel), which is held in two sets of 

 bracts and encloses within its walls a single ovule. Tliere is but one 

 silk for each ovary and there are 8oo or more ovaries on the spike. 



DEVELOPMENT OF THE EAR. Corn is a cross-pollinated 

 plant. Nature, in her efTort to accomplish this, sends out the tassel 

 as many as seven days before the silks appear on the shoot below. This 

 character is taken advantage of in mating ears in the breeding block. 

 When a pollen grain falls upon the stigma of a silk, the moisture there 

 present, and the heat of the summer causes it to germinate. 

 The external evidence of germination of a pollen grain is the produc 

 tion of a long pollen tube which penetrates the stigmatic surface and 

 passes down through the hollow style to the tip of the ovule withiq 

 the kernel. The internal evidence of germination consists in several 

 divisions of the pollen grain nucleus. Two of the resultant nuclei pass 

 down through the pollen tube, out through its ruptured tip and one 



A spikelet from the tassel cut. 

 lengthwise to show its two flow- 

 ers, the one on the right fully 

 open, the other not yet mature. 

 Sk, stalklet; C, C, outer bracts; 

 D, E, inner bracts of the open 

 flower; G, lodicules, which by 

 swelling spread the bracts 

 apart; V, F' ' , filaments cut 

 across; F, filament hearing ripe 

 anther (RA) shedding pollen 

 (P; ; YA, young anthers, the 

 left hand one cut to show, the 

 pollen. Enlarged. (Original.) 



