737 



SEED. 



SEMECARPUS. 



wedge-shaped, obtuse, entire, nearly sessile, alternate, flat, smooth ; 

 sterna decumbent ; flowers corymbose. It is a native of rocks on the 

 higher mountains of Piedmont, Savoy, Switzerland, &c. It is often 

 cultivated ill gardens. It is a trailing plant, with beautiful purple 

 flowers. It was also formerly used in medicine. 



S. acre, Acrid Stonecrop. Stems rather creeping ; branches erect ; 

 leaves ovate, fleshy, sessile, suberect, alternate, glabrous ; flowers 

 sessile, on a trifid cyme ; petals lanceolate, acuminated. It is one of the 

 most common of the gen us, and is found on walls, roofs of houses, rocks, 

 and dry places, all over Europe. When chewed in the mouth, it has 

 a hot biting taste ; hence it is frequently called Wall-pepper. When 

 applied to the skin, it produces vesication ; and, taken internally, it 

 causes vomiting. 



S. album, White Stonecrop. Branches perennial, rooting ; leaves 

 club-shaped, green, flnttish, glabrous ; cymes branched, terminal, sub- 

 corymbose ; petals bluntish. The flowers are cymose and white. It 

 is a native of Europe, in dry meadows, on walls and rocks. It is rare 

 in England. With many of the more common Stonecrops, this species 

 has been used in medicine, and also eaten cooked, or as a salad. 



SEED, in Botany, is that part of a plant which contains, within 

 several coverings, the embryo or young plant, and is itself covered 

 over with the various parts of the pericarp or fruit. The seed in its 

 young state is called the Ovule, or Seed-Bud, which is found in -the 

 interior of the Ovary, or Germen, at a very early period of its growth. 

 Vi i the ovules are first seen they are like little warty excrescences 

 mi e inside of the Ovarium, composed of delicate cellular tissue. 

 A !" ;y increase in size they elongate, and may then be divided into 

 two j<arts, a central portion, consisting of cellular tissue, called the 

 Nucleus, and an external covering consisting of two membranes, the 

 outer one of which is called Primine and the inner one Secundiue. 

 At one end the two membranes are open, forming a hole called the 

 Foramen, from which the nucleus projects more or less in the early 

 stages of its growth. As the ovule increases in size the foramen is 

 almost closed, and in the matured seed it is called the Micropyle. 

 The base of the ovule is attached to a membrane of the ovarium 

 called the Placenta, and as the ovule increases in size the portion of 

 its tissues that connects it with the ovary becomes, relatively to the 

 ovule, small and cord-like, and hence has been called the Funiculus, 

 or Umbilical Cord. The point where this cord unites with the ovule 

 becomes in the seed the Hilum, and it is at this point also that a 

 number of spiral vessels and ducts are observed to pass to the base 

 of the seed, which has been called the Chalaza. In the progress of 

 the growth of the ovule the nucleus increases in size, and becomes 

 hollow inside, forming a little shut sac, which forms a kind of third 

 membrane, called Tercine. In the interior of this sac another is 

 formed, which, as it contains or forms a part of the embryo or young 

 plant, is called the Sac of the Embryo. Whilst growing the parts do 

 not always maintain the same relations to each other that we have 

 described, and from this circumstance Mirbtl has proposed a classifica- 

 tion of ovules. When the ovule has grown regularly with the hilum 

 and chalaza at the base and the foramen at the apex, it is called a 

 Straight or Orthotropous Ovule. Although thisappearsto be the normal 

 mode of growth, it is not the most frequent. It is seen in the walnut. 

 If in the course of growth the ovule is bent round, so that the fora- 

 men is brought near to its base, where the hilum and chalaza exist, 

 it in called a Curved or Campylotropous Ovule. This is seen in the 

 Brassicacece, Papilionacett, and Caryophyllacecs. When one part of the 

 ovule grows faster than the other, the nucleus loses its relative posi- 

 tion, its point is in this instance directed towards the base, and the 

 foramen is found near the hilum, and the base of the nucleus becomes 

 situated where its apex originally was, and it carries to this point the 

 chalaza, which is continued from the cord by means of a set of vessels 

 cal lei 1 the liaphc. This forms a third class of ovules, called Contorted 

 or Anatropous Ovules. It is seen in Liliacerr, Roiaceas, Rammcitiacece, 

 &c. Mirbel maintains that all ovules are originally straight, but Link 

 doubts this. (Link, ' Grundlehren der Kriiuterkunde,' Theil ii., p. 281.) 



The position of the ovule in relation to the ovary is a point of some 

 importance in systematic botany. When it arises up from the base 

 of the ovarium, it is called Erect ; when it originates a little above 

 the base, Ascending; when it hangs from the apex of the cavity, 

 Pendulous ; when it bangs from any point below the very apex, 

 Suspended. 



Their number is also a point of value, and when there are only few 

 and easily counted, they are said to be Definite. When their number 

 is too great to be counted, they are called Indefinite. 



Such is the state of the young seed up to the time of the influence 

 of the pollen upon the stigma. Soon after this action takes place a 

 minute vesicle makes its appearance on the summit of the inner sac 

 of the nucleus. This vesicle increases in size, and is developed into 

 three parts, a descending portion, called the Radicle, and which always 

 points to the foramen; an ascending portion, the Plumule; and lateral 

 or enveloping portions, the Cotyledons ; the whole constituting the 

 Embryo, or young plant. 



Whilst the embryo is growing, the membranes which immediately 

 surround it increase in size, and frequently become the seat of the 

 deposition of a large quantity of amylaceous and other matters, called 

 Albumen, or Endosperm, which is deposited for the purpose of sup- 

 plying the young plant with nutriment during its growth. This nutri- 



HAT. HIST. DIV. VOL. IT. 



tive matter however is not always deposited around the embryo, but 

 in many cases in the cotyledons of the embryo itself, where it per- 

 forms the same functions as when deposited in the tercine, or sac of 

 the embryo. The former takes place in Raminculacece, Papaveraceas, 

 and all that group of plants named by Lindley Albuminosce, whilst the 

 latter is seen in Legumino&ce and other orders. 



When the embryo is fully grown the ovule has no further need of 

 connection with the placenta, the funiculus or cord therefore dries up, 

 and the scar which is left on the seed at its point of union with it is 

 the Hilum or Eye ; and when this is fully formed, and the embryo is 

 capable of independent growth, the ovule becomes a Seed. Sometimes 

 the umbilical cord, instead of disappearing, increases in size, forming 

 a membrane which entirely envelopes the seed, and is called an Aril. 

 One of the most remarkable instances of its existence is in the nut- 

 meg, around which a thick aril is formed, which forms the mace of 

 the shops. It is also well seen in the Euomymus, or Common Spindle- 

 Tree, where it forms a beautiful orange-coloured mantle around the 

 seed. It also exists in the Passion-Flower. Its uses are uukuown. 



The external coverings of the seed, which are called primine and 

 secundine in the ovule, are called the Testa, Perisperm, or Sperinoderm, 

 and are nothing more than a hardened state of the ovular membranes. 

 Whatever may be the number of these coverings in the ovule, they 

 are seldom discernible in the seed. In the Walnut however two inte- 

 guments can be plainly seen, one brown and tough, the other light and 

 filmy ; also in the Almond and some other seeds. In most instances 

 the testa of the seed is perfectly smooth, but in others it is covered 

 over with hair and other appendages. The cotton that is so exten- 

 sively used for the manufacture of clothing is the production of the 

 outer covering of the seeds of the cotton-plant. The Oleander is 

 supplied with hairs at a particular part of the plant, that facilitate 

 the moving of the seed from place to place through the air. In some 

 instances the seeds have broad membranous expansions of the testa, 

 called Wings, by which means they fly from one spot to another, as in 

 the Bignonia. Many seeds are beautifully marked with veins running 

 in all directions ; others have minute elevations and depressions, pre- 

 senting a remarkable regularity and beauty of structure. 



When the seed is stripped of its testa it presents either the albu- 

 men surrounding the embryo, or the embryo itself. When the albumen 

 is present, it varies much in character, being of a horny, oily, fleshy, 

 or mealy consistence. These differences depend on the nature of the 

 peculiar secretions which are mixed with fecula, or starch, in the 

 albumen. There is a peculiar form of the albumen, which is called 

 Kuminated, and which takes place in consequence of the abstraction 

 of certain parts by absorption and their not being again filled up. 

 This is the case with the Nutmeg. 



There is sometimes found in seeds an organ between the albumen 

 and embryo, which is the innermost membrane, in a state of indura- 

 tion and increased in size ; it occurs in all the species of the Ginger 

 tribe, and also in Nymphcca lutea, the Yellow Water-Lily. It is called 

 the Vitellus. 



The embryo is the most internal of all the parts of a seed. It con- 

 sists, as before stated, of the radicle, plumule, and cotyledons, to which 

 some add the Cauliculus, or Neck, which is only the point at which 

 the radicle and plumule meet. The direction which the embryo takes 

 varies much in different orders and genera of plants. Its directions 

 are divided by botanists into Absolute and Relative. The absolute 

 directions are explained by the terms straight, curved, falcate, uncinate, 

 coiled up, folded up, spiral, bent at right angles, and serpentine. Terms 

 have been devised also to express the relative positions of the embryo ; 

 but it is much more general for botanists to use the terms which we 

 have referred to in speaking of the form of the ovule, and therefore 

 we shall not explain these. 



The seed-like fruits of Lamiacece, Boraginacea?, Graminacea;, and 

 Cyperaccfc were supposed by Linnaeus and bis followers to be Naked 

 Seeds. But as these have been discovered to possess a pericarpial 

 covering, it was thought that naked seeds could not exist. This opinion 

 however has been shown by Brown to be incorrect, as he has demon- 

 strated that the seeds of Conifa'ce and Cycadacea: are from their 

 youngest state destitute of pericarp, and receive impregnation through 

 their integuments, without the intervention of style, stigma, or stigmatic 

 surface. [REPRODUCTION IN PLANTS AND ANIMALS; GERMINATION.] 



SEISU'RA (Vigors and Horsfield), a genus of Birds. 



& volitans is the Turdus volitans of Latham ; Dishwasher of the 

 colonists of New South Wales. It is constantly in motion, displaying 

 its tail and uttering a sound analogous to that made by sharpening an 

 instrument on a whetstone. 



SEIU'RUS. [SYLVIAD*.] 



SELAGINA'CEjE. [GLOBULARIACE.E.] 



SELENITE. [GYPSUM.] 



SELENIUM, a non-metallic solid elementary body, discovered by 

 Berzelius in the Iron Pyrites of Fahlun in 1818. It is not found 

 pure in nature, but in the form of selenides of the metals copper, lead, 

 mercury, and silver. [COPPER; LEAD; MERCURY; SILVER.] 



SELF-HEAL. [PRUNELLA.] 



SEMECARPUS, a very small and entirely Indian genus of Plants 

 belonging to the natural order Terebinthacece, of which the name is 

 derived from <rt\ntiov, a mark) and Kapirds, fruit, from the remarka'ble 

 property possessed by the juice of the fruit, whence it is commonly 



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