PHY 



OR, BOTANICAL DICTIONARY. 



PHY 



313 



in this the male flower parts with the stem, and swims upon 

 the water, that the aquatic animals may the sooner carry its 

 pollen to the female plant. Many foreign plants flower with 

 us, having distinctly-formed hermaphrodite flowsrs, but not- 

 withstanding bear no seeds. The climate, however, is not 

 always the cause of their barrenness, but the want of insects, 

 which nature destined in their native countries to fecundate 

 their seeds, and which we have not, along with the trans- 

 planted, received into our gardens. One experiment will 

 confirm the truth of this observation : The Abroma ctugiista 

 flowered for many years here, in a hot-house, where no 

 insects had access, without ever bearing a single fruit. The 

 gardener tried the experiment to put the pollen, by means of 

 a hair brush, upon the stigma of several flowers, and he got 

 perfectly formed fruit, which again gave him new plants. 

 In many other cases this has been done, which the limits of 

 this work will not permit us to mention. Might it not be 

 advisable for gardeners, who wish to make Cherry-trees or 

 other fruit-trees bear very early in the season, when they 

 often get little or no fruit at all, to place a bee-hive with 

 bees in the hot-house, and at the same time to take care 

 to let these busy insects get as many flowers as possible? 

 Nature seems to have given a high degree of irritability 

 to some plants, merely to promote generation. Berberis 

 vulgaris has very irritable stamens, for if they are bent only 

 a little, they instantly rebound back to the pistil. Dr. Smith 

 found that a small part of them only is possessed of this 

 irritability. Cactus tuna, has likewise a great deal of irrita- 

 bility in its stamens. If they are touched with a quill, they 

 all incline over the pistil. As soon, therefore, as insects 

 touch these irritable spots in those plants, the irritability 

 exerts itself, and stimulates the parts, and produces genera- 

 tion. Several plants have these kinds of stamens, for instance, 

 the whole family of Asclepias, &c. The elasticity of the sta- 

 mens also must in some plants produce generation, for instance, 

 in Lopezia, Urtica, Parietaria, Medicago, Kalmia, and others. 

 The style of some flowers seems to possess some degree of 

 irritability, as it follows the stamens with its stigma. The 

 shutting and opening of flowers, called their Vigilise, do not 

 belong to this subject, though by the way they may contribute 

 something to promote generation. It would appear that 

 light stimulates these parts, and produces an expansion. 

 For this reason, perhaps, most flowers open in sunshine. Por- 

 tulaca oleracea, and Drosera rotundifolia, are very powerfully 

 stimulated, and therefore open about 12 o'clock, mid-day; 

 but this violent stimulus relaxes their fibres so much earlier, 

 and they shut in an hour after. The stimulus of day-light 

 appears to be too powerful for (Enothera biennis, and it can- 

 not open till free from the influence of strong light. It re- 

 mains open during the night, from evening till morning, and 

 if the succeeding day is cool and cloudy, it will not close its 

 flowers at all. The fibre of some flowers seems to act like 

 a hygrometer, in such a manner that the flower opens by 

 means of moisture, and shuts in a dry atmosphere. This is 

 observed in all the species of Carlina. But is it the too 

 powerful stimulus of the light of the sun, which occasions 

 Nymphsea alba to close in the evening, and during the night 

 to continue immersed in the water ? Light appears also to 

 operate on the separation of the fine fragrant matter of 

 flowers, so that in some, this matter is separated merely by 

 heat and light; in others, by heat alone, and rendered percep- 

 tible to our organs of smell. It is requisite for the perform- 

 ance of generation, that the stigma be moist, and the anthers 

 covered with pollen ; if there be any medium which prevents 

 both, it cannot take place. Water does not combine with 

 the pollen, and therefore the rain washes it away : most 



flowers have such a direction, that they cannot easily be 

 affected by rain ; but notwithstanding that, We see that a long 

 continuance of rainy weather may frustrate the harvest of 

 corn and fruit. On this account, almost all aquatic plants 

 that are provided with visible blossoms, raise their flowers 

 above the surface of the water, and after the blossoming the 

 unripe fruit sinks down. Only those water plants which 

 belong to the cryptogamous class, and some few, such as 

 Najas, Caulinia, and Ceratophyllum, which have mucilaginous 

 pollen apparently capable of combining with water, evolve 

 their flowers under its surface ; it even would iseem that the 

 mucilaginous pollen of the Asclepiades, and Orcbides, perhaps 

 suffers from water. Koslreuter examined, in a very laborious 

 manner, how many grains of pollen might be required for a 

 complete impregnation. His chief discoveries on this point 

 are as follow: All the anthers of Hibiscus syriaats contained 

 4863 grains of pollen ; no more than 50 or 60 of which were 

 necessary to a complete impregnation. But "whenever he 

 took less than 50 grains, the seeds did not all ripen, but those 

 which were formed were perfect. Ten granules were the 

 least he could take in this flower, as less would not suffice for 

 it. The Mirabilis jalapa had 293 globules of pollen in one 

 flower; MirabiMs longiflara, 321 ; a<nd in each of the two 

 plants, only 2 or 3 globules were sufficient for impregnation. 

 The seeds did not appear more perfect, though many more 

 grains were put upon the stigma. To ascertain whether, in 

 flowers with several styles, each must be impregnated sepa- 

 rately, Koelreuter in several of them cut all off but one, and 

 the fecundation was as perfect as could be expected with all 

 the styles. Even in flowers, in which the style was entirely 

 separated, fecundation took place through one of them. This 

 experiment shews, that the tubes of one style communicate 

 with all the rest, and that more styles and more pollen are 

 formed, merely to ensure their determination. From this 

 circumstance philosophers have concluded, that the cellular 

 texture of all germens fixed in the receptacle, must have some 

 general connection. 



"The great and wonderful process of generation has led 

 various philosophers to form very peculiar hypotheses, which 

 each has tried to establish by a number of arguments. To 

 give an accurate account of all of them, would be transgressing 

 the bounds of our present researches ; it will suffice to men- 

 tion only the most important. The first natural philosophers 

 thought, that an accidental mixture of sohd and liquid parts 

 was sufficient to form, according to circumstances, animals 

 or plants. This was called Generatio tequivoca. Others 

 imagined, that the small animals which were observed in the 

 semen, (animalcula spermatica,) go into the ovaries of the mo- 

 ther, and thus form the future being. Others again, believed 

 that in the mother a rudiment of the future animal pre-existed, 

 to which the semen of the male imparted life. However, this 

 theory was called the system of pre-formation, or the Systemu. 

 prieformationis, pr&delineationis, or the theory of evolution. 

 These three appellations properly denoted three different 

 ideas ; but in reality they all concur in this one point, that 

 all three suppose a pre-existence of the future being in the 

 mother. Lastly, philosophers alleged, that the fecundating 

 fluids both of female and male become mixed together, and 

 thus give existence to the future animal. This theory was 

 styled, Epigenesis. The generatio arjuivoca, was supposed 

 in former times chiefly to take place in insects, worms, and 

 plants; but it is now entirely abandoned by all rational men. 

 Harve-y's doctrine is now well known, omne vivo ex ovo ; 

 farther observations of philosophers daily confirm this truth, 

 by new important observations. 1 would indeed no longer 

 notice this old theory, did not some botanists -explain the 



