THE CEREALIA. 11 



They all send up a straw or culm, which is hollow, 

 and divided into lengths by nodes or joints ; and at 

 these joints the leaves have their insertion, one at 

 each joint on the alternate sides of the stem ; each 

 leaf embraces the stem for some length in the manner 

 of a sheath. It is worthy of remark that these stems 

 always contain a portion of silex, or earth of flint, in 

 a state of very minute division from which circum- 

 stance their ashes are found useful in imparting a 

 polish to articles formed of wood, horn, ivory, or 

 some of the softer metals ; while, on the other hand, 

 the presence of this material, and the great difficulty 

 attending its separation from the purely vegetable 

 matter, have always offered obstacles to the employ- 

 ment of straw for the manufacture of paper. 



The last leaf of the season performs the office of a 

 sheath to the newly- formed flower, embracing it for a 

 time so firmly, that the sheath cannot be opened 

 without difficulty. With the growth of the flower it 

 bursts open its protecting spatha or sheath, rises 

 above it, and the leaf then turns backward. 



The head or ear consists of an uncertain number 

 of flowers, followed by seeds. These are sometimes 

 placed upon a single rib or rachis, as in wheat and 

 barley, and they then form a spike. In the variety 

 called Egyptian wheat this spike is compound, there 

 being more than one rachis ; if this consists of 

 branches that are naked at their points of junction, 

 and have spikelets at their extremities, they form 

 what is called a panicle : this is the case, for example, 

 with oats. 



The chief corn-plants, or cerealia, are wheat, rye, 

 barley, oats, millet, rice, and maize. The tribe of 

 cereal grasses is not restricted to these seven varie- 

 ties, but includes numerous others, which, if they are 

 not equally employed as food, are neglected only on 

 account of the smallness of their seeds. ' None are 



