When, on the other hand, the taproot grows slowly
or ceases its growth, and the numerous secondary roots grow long, a
fibrous root system results, which is characteristic of the cereals,
grasses, corn, and other similar plants. With any type of root, the
tendency of growth is downward; though under conditions that are not
favorable for the downward penetration of the roots the lateral
extensions may be very large and near the surface
Extent of roots
A number of investigators have attempted to determine the weight of
the roots as compared with the weight of the plant above ground, hut
the subject, because of its great experimental difficulties, has not
been very accurately explained. Schumacher, experimenting about
1867, found that the roots of a well-established field of clover
weighed as much as the total weight of the stems and leaves of the
year's crop, and that the weight of roots of an oat crop was 43 per
cent of the total weight of seed and straw. Nobbe, a few years
later, found in one of his experiments that the roots of timothy
weighed 31 per cent of the weight of the hay. Hosaeus, investigating
the same subject about the same time, found that the weight of roots
of one of the brome grasses was as great as the weight of the part
above ground; of serradella, 77 per cent; of flax, 34 per cent; of
oats, 14 per cent; of barley, 13 per cent, and of peas, 9 per cent.
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