SEMEN, in botany, the SEED; the essence of the fruit of every vegetable; defined by Linnæus to be a deciduous part of the plant, containing the rudiments of a new vegetable, and fertilized by the aspersion or sprinkling of the male-dust. The parts of a seed, properly so called, enumerated by Linnæus, are as follows: 1. CORCULUM, the punctum vitæ, or essence of the seed. 2. COTYLEDONES, the lobes. 3. HILUM, a mark or scar in the seed. 4. AXILLUS, Lin. the proper covering: calyptra of Tournefort. 5. CORONULA, PAPPUS, the crown of the seed. 6. ALA, the wing of the seed.
Besides the seed properly so called, two other terms are referred by Linnæus to the general article of SEMEN, viz. 7. NUX, a nut, or seed covered with a hard bony skin. 8. PROPAGO, the seed of the mosses.
With respect to number, plants are either furnished with one seed, as sea-pink and bistort; two, as wood-rose and the umbelliferous plants; three, as spurge; four, as the lip-flowers of Tournefort and rough-leaved plants of Ray; or many, as ranunculus, anemone, and poppy.
The form of seeds is likewise extremely various, being either large or small, round, oval, heart-shaped, kidney-shaped, angular, prickly, rough, hairy, wrinkled, sleek, or shining, black, white, or brown. Most seeds have only one cell, or internal cavity; those of lesser burdock, valerian, lamb's lettuce, cornelian cherry, and sebesten, have two.
With respect to substance, seeds are either soft, membranaceous, or of a hard bony substance; as in gromwell, tamarind, and all the nuciferous plants.
In point of magnitude, seeds are either very large,
Semen. as in cocoa-nut; or very small, as in campanula, ammannia, rampions, and throat-wort.
With respect to situation, they are either dispersed promiscuously through the pulp, (semina nidulantis), as in water-lily; affixed to a future or joining of the valves of the seed-vessel, as in the cross-shaped and pea-bloom flowers; or placed upon a placenta, or receptacle within the seed vessel, as in tobacco, and thorn-apple.
Seeds are said to be naked (semina nuda) which are not contained in a cover, or vessel: such are those of the lip and compound flowers, the umbelliferous and rough-leaved plants; covered seeds (semina tecta) are contained in some vessel, whether of the capsule, pod, berry, apple, or cherry kind.
A simple seed is such as bears neither crown, wing, nor downy pappus; the varieties in seeds, arising from these circumstances, are particularly enumerated under their respective heads.
In assimilating the animal and vegetable kingdoms, Linnaeus denominates seeds the eggs of plants. The fecundity of plants is frequently marvellous; from a single plant or stalk of Indian Turkey wheat, are produced, in one summer, 2000 seeds; of elecampane, 3000; of sun-flower, 4000; of poppy, 32,000; of a spike of cat's-tail, 10,000 and upwards: a single fruit, or seed-vessel, of tobacco, contains 1000 seeds; that of white poppy, 8000. Mr Ray relates, from experiments made by himself, that 1012 tobacco-seeds are equal in weight to one grain; and that the weight of the whole quantum of seeds in a single tobacco-plant, is such as must, according to the above proportion, determine their number to be 360,000. The same author estimates the annual produce of a single stalk of spleen-wort to be upwards of one million of seeds.
The dissemination of plants respects the different methods or vehicles by which nature has contrived to disperse their seeds for the purpose of increase. These by naturalists are generally reckoned four.
1. Rivers and running waters. 2. The wind. 3. Animals. 4. An elastic spring, peculiar to the seeds themselves.
1. The seeds which are carried along by rivers and torrents are frequently conveyed many hundreds of leagues from their native soil, and cast upon a very different climate, to which, however, by degrees, they render themselves familiar.
2. Those which are carried by the wind, are either winged, as in fir-tree, trumpet-flower, tulip-tree, birch, arbor-vitæ, meadow-rue, and jessamine, and some umbelliferous plants; furnished with a pappus, or downy crown, as in valerian, poplar, reed, succulent swallow-wort, cotton-tree, and many of the compound flowers; placed within a winged calix, or seed-vessel, as in scabious, sea-pink, dock, discorea, ash, maple, and elm-trees, logwood and weald; or lastly, contained within a swelled calix or seed-vessel, as in winter-cherry, cucubalus, melilot, bladder-nut, fumitory, bladder-fena, heart-feed, and chick-pease.
3. Many birds swallow the seeds of vanelloe, juniper, mistletoe, oats, millet, and other grasses, and void them entire. Squirrels, rats, parrots, and other animals, suffer many of the seeds which they devour to escape, and thus in effect disseminate them. Moles,
ants, earth-worms, and other insects, by ploughing up the earth, admit a free passage to those seeds which have been scattered upon its surface. Again, some seeds attach themselves to animals, by means of hooks, crotchets, or hairs, which are either affixed to the seeds themselves, as in hound's tongue, moult-eat, vervain, carrot, bastard-parly, sanicle, water hemp, agrimony, aristeus and verbesina; to their calix, as in burdock, agrimony, rhexia, small wild bugloss, dock, nettle, pellitory, and lead-wort; or to their fruit or seed-vessel, as in liquorice, enchanter's night-shade, cross-wort, elixers, French honey-suckle, and arrow-headed grass.
4. The seeds which disperse themselves by an elastic force, have that force resident either in their calix, as in oats and the greater number of ferns; in their pappus, as in centaurea crupina; or in their capsule, as in geranium, herb-bennet, African spirea, fraxinella, horle-tail, balsam, Malabar nut, cucumber, elaterium, and male balsam apple.