30 apes CEREALS 
other cereals. It is a native of northern Asia where doubt- 
less it has been cultivated for a long time; yet its introduc- 
tion into other regions was comparatively recent. Like rye 
its chief merit is that it will yield a profitable crop on very 
poor soil. The flour made from it, however, is correspond- 
ingly poor in nutritive value. It is usually mixed with other 
sorts of flour to which it imparts an agreeable flavor. 
25. The value of cereals. Why is it that the cereal grains 
have been valued so highly from the earliest times? What 
makes them so much better than other vegetable foods, 
and why are some of them superior to others? The fact 
that these plants ripen their seeds within a few months after 
planting, and under favorable conditions yield such a large 
return for the labor bestowed upon them, will doubtless 
partly account for the high favor in which they are held; 
but as much the same may be said of other vegetables of far 
less value as food, there must be some more important 
reasons. In order to understand these, we must know some- 
thing of the chemical composition of cereals; that is to say, 
we must learn what substances are to be found in the differ- 
ent grains and in what amount. , 
26. Water in grains. Every part of a plant contains or- 
dinarily a certain quantity of water—succulent herbage and 
fruits like the watermelon having a great deal, while woody 
parts, seeds, and grains have comparatively little. The — 
quantity of water contained in a given specimen, is esti- | 
mated by drying a known weight of the material at the tem- 
perature of boiling water, and then reweighing to find how 
much has been lost: the loss will be practically equivalent to 
the weight of water originally present. In the Food Chart on 
page 114 the student will find indicated the average percent- 
age of moisture in each of the cereals and in various other 
vegetable foods as commonly found in the markets. A 
glance will show what a comparatively small amount the 
cereals contain. For this reason they keep remarkably well 
when stored, and take up very little room in proportion 
to the amount of nutriment they afford. 
27. Ash. If the sample dried as suggested be burned 
until all of the combustible material is consumed, there will 
