50 PLANT BKEEDING. 



well. Without dissemination under some such system as the above, 

 experiment stations would hardly be justified in breeding many of 

 the staple crops, sinc(^ only through successful methods of distribu- 

 tion do the farmers of the State receive any benefit. 



WHEAT FLOWERS. 



The floret is the most interesting part of the wheat plant. Figure 

 15 shows the separate parts of the flower, also the spike and the seeds. 

 The floral plan is shown by the ci'oss section at 5, where the flowering 

 glume (/(/) and the palea {p) are folded about the three anthers (a) 

 and the stigma (s). Before the flower is mature the anthers are closely 

 packed about the stigma in the bottom of the floral cavity, as shown 

 in Jf.A. At the maturity of the flowers the anthers are shoved upward, 

 some of them passing out of the floret, as at JfB. The floret usually 

 opens about dawn, and closes again within an hour. This is shown 

 in figure IG, where the opening of the anthers is also illustrated, as 

 shown in Ji-B (fig. 15). In passing upward the pollen sacs break 

 open, and before the anthers reach the outside of the floret some pol- 

 len falls back on the stigma. As the floret matures the stigma 

 changes from its folded form, as shown at 12 (fig. 15), and expands 

 into a plume {13). The pollen grain is a minute ronnd male cell {11, 

 fig. 15), which, falling upon one of the minute branches of the stigma 

 {13), " germinates " and sends a tube into its tissues {18). This pollen 

 tube, growing downward, enters the ovary {13 o), where its nucleus 

 fuses with the female nucleus in the ovum, and from this fusion tlie 

 embryo of a new plant arises. The stigma, having served its purpose, 

 withers, while the ovary begins developing {14, s and o), and in a few 

 weeks a mature seed fills the floral cavity. The seed has a ventral 

 and a dorsal side, as shown in 15, 16, and 17. At the bottom on the 

 dorsal side is the germ, sometimes called "chit," the miniature plant, 

 which is ready when planted to use the remaining portions of the 

 kernel, the endosperm, as food while it sends leaves into the air and 

 roots into the soil, establishing itself so that it can grow into a useful 

 plant, multiplying itself many fold. 



FORMATION OF VARIETIES BY HYBRIDIZING. 



Hybridizing is used to produce plants with greater tendency to 

 variation. Hybrids are made between numerous varieties of wheat, 

 and in each case large numbers of florets are handled. . Great care is 

 exercised to secure superior plants of the varieties hybridized, and as 

 a rule plants are chosen from the best centgener stocks which are 

 under improvement by selection from the most useful standard parent 

 wheats, as mentioned above. In i^reparing a good spike of wheat for 

 hybridizing, all but one or two dozen strong florets in the center of 

 the spike are removed by means of sharj) scissoi's, as shown in figure 

 17. (See also PI. Ill, fig. 2.) The anthers are removed from these 



