PHY 



OR, BOTANICAL DICTIONARY. 



PHY 



315 



1 



it beyond doubt that two sexes exist in plants. Every person 

 may, indeed, easily convince himself of the fact, by repeating 

 such experiments on the pecies of Melon and Gourd; and 

 every where in the vegetable kingdom he will find two distinct 

 sexes. The seed already exists in the germen during the 

 time of blooming, before fecundation takes place, and contains 

 a very clear liquor, called, by Malpighi, the Chorion. With 

 this, most likely, the fecundating particle of the male semen 

 is mixed, and thus produces the embrio of the future plant. 

 Koelreuter, however, thinks that the moisture of the stigma, 

 which he, according to his favourate idea of an oily impreg- 

 nating fluid in vegetables, supposes likewise to be oily, is 

 mixed with the fluid of the male, and that these two combined 

 are conveyed into the seed. However, be this as it will, 

 great alteration is observed to take place in the seed sooner 

 or later after fecundation, according to the variety of plants. 

 For in the neighbourhood of the navel a small vesicle appears, 

 filled with some liquid. The vesicle is called the sacculus 

 colliquamenti ; and the liquor in it, the amnios. This vesicle 

 grows larger, absorbs the chorion, which at last entirely dis- 

 appears, so that the cuticle finally becomes the membrana 

 interna of the seed. The amnios grows hard, and forms the 

 cotyledons. As soon as the vesicle shews itself, the embryo 

 of the future plant likewise appears gradually, which consists 

 in the corcle. It is formed gradually, and becomes visible in 

 the Sun-flower, (Helianthus annuus,) three days after impreg- 

 nation ; in the Cucumber, (Cucumis sativus,) a week after; 

 and in Meadow Saffron, (Colchicum autumnale,) some months 

 after. It is flaky in the beginning, but in time becomes, like 

 the vesicle which contains it, larger and firmer. The vesicle 

 does not in all seeds increase in the same form ; in some it 

 grows larger in its whole circumference, in others it grows 

 longer towards one extremity, which runs straight out to the 

 opposite end, and the sides are extended. Thus the seed 

 comes to maturity, and when perfectly ripe, separates in dif- 

 ferent ways from its mother plant, and begins a new life itself, 

 passing through all the scenes again, just now explained. 

 This is the common way in which plants are propagated. 

 But we have plants, which do it in another way besides evolv- 

 ing their seeds. At the stem, or near the angles of the leaves, 

 by nature, or even through accident, the spiral vessels of plants 

 form sometimes knots, which become buds, and separating 

 spontaneously from the plant itself, send out roots and leaves, 

 thus forming an entirely new plant of the same species. Such 

 plants are called viviparous plants, (vegitabilia vivipara.) 

 Several species of Garlic, (Allium,) the Lilium bulbiferum, 

 Poa bulbosa, and other plants, do this spontaneously. The 

 garden Tulip, (Tulipa gesneriana,) exhibits this curious phe- 

 nomenon by means of a simple manoeuvre of art, if the flower 

 is cut off before impregnation has taken place, and the stem 

 with the leaves be allowed to remain, provided it be in a 

 shaded spot. Several succulent plants, for instance, Eucomis 

 punctata, do it when treated in the above manner. Gardeners 

 increase plants by layers, suckers, grafts, and inoculation, in 

 a similar'manner. The bud of a tree or shrub, when grafted 

 into another stock, will there be unfolded, and must indeed 

 be regarded as a different plant altogether. It is not changed 

 in its nature, but grows as if placed in the earth; the stem 

 only serves to convey the imbibed sap to it, which it must 

 itself digest according to its nature. Agricola and Barnes, 

 it appears, were more successful in these operations, for they 

 placed buds directly in earth, and produced perfect plants. 

 It is remarkable in this kind of artificial increase, that where 

 branches or buds are in any way formed into new plants, by 

 layers, grafts, or inoculation, the plant from which they were 

 taken does not propagate as species, but only as variety. If 

 VOL. ii. 92. 



we take the part of an individual, and convert it into a parti- 

 cular plant, in this way all the varieties may be multiplied. 

 The seed therefore propagates only the species which may 

 grow, from it under many different appearances as varieties: 

 but in the branch, as in the bud, the germ is already formed, 

 and it is totally impossible that the shoot issuing from them 

 can alter in the least. Thus is the Apple of Borstdorf pro- 

 pagated by grafts: inoculation will always remain the same, 

 but from the seed will be obtained many varieties entirely 

 different. 



" The stem of ligneous plants, annually adds a new ring of 

 vessels. The first circles begin to become ligneous on their 

 sides. The wood has, in general, when young, a yellowish 

 white colour, which, according to the species of the plants, 

 assumes a darker hue every year. The quick circulation of 

 the sap takes place only in the young vascular circles; in the 

 older ones the sap is carried along much slower, and they 

 have their irritability greatly diminished. The life of every 

 shrub or tree consists only in the young rings of these vessels, 

 which is called inner bark, and the plant must die when this 

 is wounded. Thus, if a ligneous plant has performed its 

 offices for a number of years, then the innermost ring begins 

 to be obstructed, and to become more and more dense; this 

 occasions that those lying next them no longer obtain their 

 moisture from them. They therefore begin to move their 

 sap slower, and the youngest vascular circle becomes gradu- 

 ally thinner and thinner. At last the sap stops likewise in 

 the following ligneous ring; the young vascular circle cannot 

 form itself completely; few buds are now unfolded; the 

 small number of leaves cannot prepare sufficient sap for the 

 whole; and the common certain lot of organized bodies, death, 

 sets the final insurmountable bound to vegetation. In herba- 

 ceous plants all the vessels of the stem become dry and hand 

 in one year; and as they can no longer convey the sap, con- 

 sequently the stem decays at the end of the year. Their 

 root forms, as the stem of ligneous plants does, annually a 

 new vascular circle, and it dies in the same manner, when all 

 those circles have become too ligneous. But such herbs, the 

 roots of which are annually renewed, are of constant duration. 

 The old root dies, its fibres being entirely ligneous ; but a 

 new one appears, and is to be considered as a young plant. 

 Herbs, whether they live one year only, as the annual plants, 

 or two years, as biennial plants, become so exhausted by the 

 formation of the flower and fruit, that the irritability of their 

 vessels becomes much impaired ; they therefore become quite 

 ligneous, and the root and stem must decay after their fruits 

 are ripened. They may, however, be preserved for several 

 years, if their flowers, when in the bud, be taken off. The 

 same happens when their flowers are filled, in which case 

 fecundation does not take place, and consequently no fruit 

 is formed. These vessels retain that irritability which is 

 necessary for their duration, and which would have been lost 

 by the wasting of their strength, and their fibres become lig- 

 neous more slowly. Natural death is not the same in all 

 vegetables: as in all organized bodies, it ensues in three 

 ways. First, by the induration of the fibre; as in trees, 

 shrubs, and under-shrubs. Secondly, by the powers being 

 exhausted; as in annual and biennial plants. Lastly, by 

 dissolution; as in soft Fungi, and the species of Boletus. 

 These plants imbibe a great quantity of moisture, which in- 

 creases with their age. In them no part becomes ligneous; 

 but they die in too softened a state, and putrefy from a super- 

 fluity of moisture. The duration of life differs greatly in 

 different plants. Some species of Boletus require only a few 

 hours for their evolution, and as soon again decay. Several 

 Fungi live only a few days, others weeks and months. Annual 

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