. Elements of biology; a practical text-book correlating botany, zoology, and human physiology. Biology. spread of some of our worst weeds in this way. The burdock and clotbur are familiar examples. In both the mass of little hooks is all that remains of an involucre. Thus the whole fruit cluster may be carried about and seeds scattered. In many other fruits of the compos- ites, as in the cockleburs and beggar's ticks, the whole fruits are provided with strong curved projections which The cockiebur. bear many smaller hooklike barbs. Fxamine the front of a cockiebur or a beggar's tick with a lo
. Elements of biology; a practical text-book correlating botany, zoology, and human physiology. Biology. spread of some of our worst weeds in this way. The burdock and clotbur are familiar examples. In both the mass of little hooks is all that remains of an involucre. Thus the whole fruit cluster may be carried about and seeds scattered. In many other fruits of the compos- ites, as in the cockleburs and beggar's ticks, the whole fruits are provided with strong curved projections which The cockiebur. bear many smaller hooklike barbs. Fxamine the front of a cockiebur or a beggar's tick with a low magnifica- tioii or even a hand lens. Draw such a fruit. Of what probable use are the many barbs? Pappus. — Probably the most important adaptations for dis- persal of seeds are those by which the fruit is fitted for dispersal by the wind. That much-loved and much-hated weed, the dande- lion, gives us an example of a plant in which the whole fruit, an achene, is carried by the wind. The parachute, or pappus, is an outgrowth of the ovary wall. Many other fruits, notably that of the Canada thistle, are provided with the pappus as a means of getting away. If dan- delions are available, notice the wonderful lightness and strength of the pappus. In the milkweed the seeds have developed a silky outgrowth which may carry the seeds for miles. In New York city the air is some- times full of the down from these seeds which is brought from far over the meadows of New Jersey by the prevailing westerly Dandelion heads; the middle one a of ripe fruits ready to be scattered by the wind. Photographed by Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Hunter, George William, 1873-1948. New York, American book company
Size: 1659px × 1506px
Photo credit: © Paul Fearn / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., boo, bookpublishernewyorkamericanbookcompany, booksubjectbiology
