24 COMPARATIVE STUDY OF CEREALS 



should be made of a typical grass first, and then all the cereals in 

 comparison. 



The Spikelet. The central part of the wheat head is called a 

 racliis. On the rachis are the spikelets. If the spikelets are attached 

 directly to the rachis, so a compact head is formed, as in wheat, the 

 whole is called a spike. If the spikelets are on long branches, as in 

 oats, the whole is called a panicle. The typical grass spikelet is made 

 up of two empty glumes and one or more fertile flowers above 

 (Fig. 10). 



i 1 



FIG. 10. Comparative study of spikelets. From left to right the spikelets shown 

 are, brome-grass, barley, rye, oats, wheat, corn. Below are shown the two empty glumes in 

 each case. In corn the glumes are much reduced, but a careful study will show analogous 

 parts in all spikelets. 



The Flower. A grass flower consists of one fertile glume or 

 "flowering glume, and palet enclosing one ovary and three stamens. 

 A careful comparison will show that all the cereals conform to the 

 above description, except in corn, where the stamen flowers and ovary 

 flowers are separated, but are otherwise similar. 



Fertilization. When the time has arrived for the flower to be 

 fertilized, the glumes open and the stamens come out. The pollen sacs 

 burst, freeing the pollen in the air. At about the same time the 

 stigmas spread out to receive pollen. When a pollen grain drops on 

 a stigma the contents of the pollen grain immediately pass into the 



