3o6 



BOTANY OF CROP PLANTS 



of five parts united below to the base of the ovary (Figs. 123 

 and 124). There are five stamens opposite to and partially 

 attached to the perianth ring. The ovary is half-inferior, 

 that is, partially imbedded in the flesh of the receptacle, one- 

 celled and one- to three-seeded. There are two to three 

 short, awl-shaped stigmas, united at the base. 



Pollination and Fertilization.^ — The beet flower is protan- 

 drous. Shaw has shown that "self-fertilization " (autogamy) 

 does not take place, and that "close 

 fertilization" (geitonogamy) is usu- 

 ally ineffective. He has also demon- 

 strated that thrips voluntarily travel 

 from plant to plant, and positively 

 assist in polUnation of beet flowers. 

 Bees are of little consequence in this 

 process. Wind is the chief factor in 

 beet pollen dissemination. 



Fruit and Seed. — The ripened 

 ovary of each flower is imbedded 

 in the receptacle and the base of the perianth. The 

 fruit is hard and nut-like, and contains a single, dark, 

 smooth seed. The beet seed of the market is frequently 

 called the "seed ball." The "seed ball" usually contains 

 a number of germs; however, in some cases a single germ 

 is produced. The multiple-germ beet seed arises when the 

 flowers are in clusters; in this case, the parts of the several 

 flowers stick together forming a several-seeded mass, the 

 "seed ball." If the flower stands by itself on the stem, a 

 single-germ beet seed is produced- The single flowers are 

 usually located at points on the stem where a branch arises. 

 According to this, a highly branched inflorescence will 

 produce a greater proportion of single flowers. 



Tests of the comparative yields of beets from single-germ 



I mm 



Fig. 124. — Diagram of 

 beet flower, showing one- 

 half of flower cut length- 

 wise. (After Townsend and 

 Ritlue. U. S. Dept. Agri.) 



