18 BULLETIN 503, U. S. DEPARTMENT OF AGRICULTURE. 
stances, which give the plants their characteristic flavor and odor. 
Mineral matter is an important constituent of these vegetable foods, 
the proportion, though small, being about the same as is found in 
many other common articles of diet. Sodium, potassium, iron, sul- 
phur, and phosphorus compounds are the common mineral con- 
stituents. As the mineral matters exist in combination with organic 
acids and other bodies, they contribute materially to the flavor of the 
tubers, roots, etc. 
Beets, carrots, parsnips, salsify, turnips; and onions are the most 
common of the so-called succulent root crops used as food. They 
differ from starch-yielding vegetables like potatoes mainly in con- 
taining a larger proportion of water, 85 to 90 per cent on an average, 
and consequently a smaller proportion of nutritive material. Further- 
more, it is generally true that starch is not the characteristic carbo- 
hydrate of these vegetables, its place being taken by sugars of differ- 
ent sorts, pectose bodies, and other similar carbohydrates, while the 
percentage of crude fiber is also rather higher than in the edible 
starch-yielding roots and tubers. Many of the vegetables included 
in this group are characterized by marked flavors and odors due to 
the presence of volatile organic sulphur compounds in their juices. 
In the members of the onion tribe these are especially strong, and 
some varieties are used almost exclusively as flavoring materials, 
while other and milder sorts are also used: in large quantities as table 
vegetables. 
Though not very nutritious in proportion to their bulk, root crops 
as a class offer some advantages over most other vegetable foods. 
They are so easily grown and so productive that under ordinary con- 
ditions they sell at prices within the reach of all. Many of them 
may be kept over winter in such good condition that they are prac- 
tically never out of season, or are in season when other vegetables are 
scarce. The carbohydrates, the principal nutritive material present, 
are in forms which are readily and well assimilated. The character- 
istic flavor which some of these vegetables possess is a decided ad- 
vantage, as it makes the vegetables palatable and adds to the variety 
of the diet. Succulent vegetables of all sorts contribute bulk to the 
diet and so are valuable from the standpoint of hygiene, because 
within limits bulkiness is a favorable condition for normal digestion 
and also of importance in overcoming a tendency to constipation. 
They are among the important sources of necessary mineral matters 
in the ordinary diet. Since the body performs its functions best if 
its tissues and fluids are either neutral or slightly alkaline, and since 
vegetables tend to produce that effect, they have a special value as 
regulators of the body processes. 
