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wheat, 53 flax, 43 buckwheat, and 91 ragweed seeds. The wind was blowing at the rate of 20 miles per hour. There can be no question but that a drift holds a large number of weed seeds. Along our highways one may find, where the snow has drifted, the ragweed and thistle growing in large numbers.
Water.—A number of our very troublesome weeds are carried by the water. This is notably true for the “seeds” of docks. Three of the sepals or outer floral envelopes of the flower of the docks each bear an enlarged body called the tubercle, which is hollow. This body, combined with the calyx, enables it to float on the water. During our recent wet years, it has been noticed by farmers that these docks are unusually common on low ground, having been carried thither by water. Many seeds, like those of pepper grass, are mucilaginous. In
walking through a patch of this weed
stick-seed, burdock, sandbur, and tick trefoil. Explosive Properties.—We have but one weed the
seeds of which have explosive properties. This is the
yellow sorrel (Oxalis), which is com
mon in some fields. The outer coat of the seed separates and the seed is forced out of the pod as though
shot from it.
Creeping Mechanisms.-The needle-grass is important as a weed at times only, in gravelly pastures. The seed of this grass has a sharppointed callus and hairs above this point that project obliquely upwards.
this way the seed not only creeps
Fig. 11. The seedlike - - fruit of arrow-head, It has a long, twisted awn, and in scattered by water.
over the ground, but becomes buried. The wild oats also has a creeping arrangement. Man as an Agent.—Nursery stock is responsible for the scattering of a number of weeds and weed seeds. The scattering of quack grass in this way had been reported to us. Canada thistle, ox-eye daisy, and other perennial weeds are known to have been carried and scattered by this means. Wool.—Wool is often responsible for the introduction of a great many different weed seeds. Around woolen mills it is common to find Fuller's teasel, which is so commonly used in carding of wool. The western storksbill o (Erodium cicutarium) no doubt owes its Fig. 12. Seeds origin in this section to having been :*::::"... o: introduced with wool. There is con- containing seeds of Stant danger when getting live stock Poison ivy, ... etc. from the o o # weeds of (U. S. Dept. Agrl.) this character will be introduced. Some members of the borage family like Lappula floribunda have been scattered in this way. Cultivation.—It is not uncommon to find that weeds are carried from one field to another by cultivators or plows. This is particularly true of quack grass and Johnson grass. Impure Seed.—Many bad weeds are introduced with impure seed. We have during the past season received many specimens of weeds found in clover meadows. These weeds were undoubtedly introduced with clover seed. In nearly all instances the farmers stated that they had not observed these weeds before. Not all of the clover seeds sold by seed merchants contained these weed seeds, much of it being of good quality.
As examples of presence in clover fields of weeds introduced with seed, a few selected areas observed July, 1903. may be cited. Three areas Io feet square situated southwest of Ames averaged 53 vigorous specimens of ribgrass. Two areas 12 feet square upon a farm near Mar