PHY 



OR, BOTANICAL DICTIONARY. 



PHY 



311 



or by the transpiration of a fine volatile oil. If this blooming 

 plant is in abundance, and about this time is moved suddenly 

 through an extended space, and if immediately adjoining 

 there be a piece of burning paper, a fine blue flame, which 

 may be easily extinguished, is instantly emitted. The 

 daughter of Linneus observed in the Tropeeolum majus, and 

 other flowers of a deep orange colour, an electric spark, 

 during the dark and serene warm summer evenings. The 

 nectaries, when they do not consist of mere glands, agree in 

 structure with the corolla. The stamens consist of the fila- 

 ment and anther. They are likewise called the male organs 

 of generation. The filament, in the distribution of its ves- 

 sels, sometimes resembles the herbaceous stem, sometimes 

 the leaves, according to the variety of its shape, which dif- 

 fers very much, but in each plant commonly bears a peculiar 

 and constant character. The anthers are formed of a thin 

 but vascular membrane, filled with pollen. The pollen 

 occurs under a variety of forms, which can be seen only 

 with a microscope. Jussieu, Duhamel, Needham, Gleichen, 

 and others, observed with a high magnifying microscope, 

 that the grains of the pollen, when brought in contact with 

 water, burst with a degree of violence, and emit a gelatinous 

 mass. . Koelreuter, on the contrary, assures us, that ripe 

 pollen does not burst suddenly when wetted, but slowly 

 emits through its pores, or, if provided with small prickles, 

 through those, an oily fluid, which on the surface of water 

 forms a distinct shining pellicle. He says further, that each 

 single granule of the pollen consists of two membranes ; an 

 external one, which is thick, elastic, cartilaginous, and full 

 of very delicate vessels, in which last are the pores which 

 emit the oily liquid; and secondly, an internal very fine mem- 

 brane. The internal surface is lined with a very tender, elastic, 

 cellular texture, which contains the oily impregnating mass. 

 Hedwig, however, after his latest researches, dots not agree 

 with Kffilreuter. He says, that each granule of the pollen 

 consists of one vascular membrane only, filled in its interior 

 with a gelatinous mass, but has no cellular texture whatever; 

 and, according to him, the pollen emits this fluid at once- 

 it does not exude out through pores. Hedwig examined 

 that portion of pollen, which had on the female stigma per- 

 formed its functions, and he found this observation confirmed. 

 Even the stamens of the Mosses are, according to him, only 

 granules of pollen acting as the others. He finds a great 

 similarity between this fructifying mass and the semen of 

 animals; only that, as well as in the animal kingdom, it 

 differs in consistence in different species. Most observations 

 indeed coincide in this, that the moisture which is contained 

 in the pollen, is not oil, but a mere gelatinous mass, which, 

 however, cannot easily be mixed with water. It is, however, 

 likewise proved by experience, that this mucus contains a 

 considerable quantity of oil, for an oil may be obtained from 

 the pollen by pressure, as it takes fire when thrown into a 

 flame, and, finally, bees prepare their wax from it. It does 

 not however follow, that the whole is oily ; for an almond 

 cannot be called merely an oily substance because oil may 

 be obtained from it; it contains this oil in a gelatinous mass. 

 As in the animal kingdom, a more important question, What 

 constitutes the impregnating power of the pollen, or on what 

 does it depend? remains still unanswered. Is it a subtile 

 oily vapour, or a subtile volatile aura? or is it, according 

 to others, electricity, or any other power? Still we are here 

 in the dark. The female organs of fructification are the 

 pistil, which consists of the germen, the style, and the stigma. 

 The germen varies in its shape and structure in various 

 plants. It is composed of all those vessels which we noticed 

 in the rest of the plant ; their direction and distribution only 

 , VOL. ii. 92. 



differ in each. The seeds, if the germen itself does not 

 become a seed, are situated in it, and are connected with it 

 by the umbilical cord. In its interior, it contains a clear 

 fluid, in which nothing particular can be perceived. When 

 the germen is converted into a seed, the umbilical cord hangs 

 together with the receptacle, and is very short. The internal 

 structure of such a germen, is the same as that of the seed 

 contained in the germen. The style appears under a variety 

 of shapes. All the known vegetable vessels compose it, and 

 it has hollow tubes, which at the top are, by a tender cellular 

 texture, connected with the surface of the germen, and with 

 the cord of the seed. Hedwig, in his microscopical researches, 

 found in the species of gourd, and its kindred plants, on the 

 stigma, hollow channels, in which he detected a firm, yellow, 

 gelatinous body, which in the gourd was quadrangular, ran 

 through the whole extent of the style, and ended in the 

 umbilical cord of the seed. It appeared impenetrable, and 

 incapable of carrying any fluid. But as, unquestionably, it 

 contributes to the fecundation of the pollen, either as a con- 

 ductor or as a conveying medium, he calls it conductor fruc- 

 tificationis. Its use, however, is yet concealed from us ; 

 and it is even not yet precisely ascertained, whether other 

 plants have it, or if a different regulation in them answers 

 the same purpose. The stigma consists of hollow absorbent 

 channels, the structure of which is observable only with the 

 microscope. Those absorbent channels or tubes constitute 

 the stigma. The pappus, which is met with in compound 

 flowers, and which exists completely formed in the ripe seeds, 

 is certainly not to be considered, with Rafn, as a mere inor- 

 ganic lifeless fibre. To me, it appears to consist of large 

 elongations of the secondary vessels, which contribute a great 

 deal to the condensation and proper preparation of the sap. 

 They, indeed, grow themselves at the very period they per- 

 form these functions; when, therefore, the seed has attained 

 its proper size, the vessels of the pappus become plugged up, 

 and it remains dry upon the seed. The stigma, now in its 

 state of puberty, or when fit for impregnation, is covered 

 with a fluid, which Koelreuter likewise considers as oily, 

 but the nature of which is not yet investigated. The period 

 when the stigma is inoist and the anthers burst, is the period 

 of impregnation. This copulation, however, is in plants 

 performed in so very striking a manner, that we cannot con- 

 template without admiration the wise measures which nature 

 has taken for the accomplishment of her designs. 



" Most flowers are hermaphrodite, or such as have both male 

 and female organs of generation ; and one would from this cir- 

 cumstance be led to believe, that in such flowers impregna- 

 tion is readily completed ; this however is not the case with 

 all. Mr. Sprengal has made many observations on this point, 

 most of which are highly important. He discovered two 

 principal ways in which seeds are impregnated, to wit, 

 Dichogamy, and Homogamy. He calls it Dichogamy, when 

 in a hermaphrodite flower one organ of generation is 

 first evolved, and when this has lost its generative power, 

 the other organ arrives at perfection. This is again of a 

 twofold kind. Either the male parts are formed perfectly, 

 before (he female parts unfold themselves, which he calls 

 Dichogamia androgyna; or it is the reverse, the female parts 

 being first formed. This he styles Dichogamia gynandra. 

 Homogamy is, when both parts of generation are formed in 

 a hermaphrodite flower, exactly at the same period. Now, 

 in a hermaphrodite flower, when Dichogamy takes place, 

 impregnation cannot naturally happen without intermediate 

 means, by which both organs of generation may be brought 

 near each other. Linneus thought that the wind performed 

 this, but there are few plants where wind could do it. as 

 4K 



