OF FECUNDATION. 



87 



with nature, in the greatest number of cases ; 

 hut there ai'e other circumstances in which tlie 

 phenomena of fecundation are not produced in 

 the same manner. In plants which are always 

 sii bmersed, it is evident that the grains of pollen 

 do not attach tliemselves to the stigma and burst 

 uj on it ; yet fecundation takes place in them as 

 in other plants. The surl'aco of the stigma of 

 many plants is extremely smooth, and by no 

 means clammy. That of the chestnut is hard 

 and leathery. In these plants, the pollen cannot 

 adhere to the stigma. In many of the orchis 

 tribe, the pollen, in place of presenting a pow- 

 dery substance, composed of an innumerable 

 multitude of minute and light particles, forms 

 an entirely solid mass. The anther opens ; the 

 mass of pollen retains its place, and remains 

 nerfectly entire ; and yet fecundation is effected. 

 Now, in this case, the pollen has not left the 

 interior of the anther to be can-ied to the stigma, 

 and there pour out its fecundating fluid. By 

 the opening of the anther, it is merely placed in 

 contact with the atmospheric air, and yet the 

 plant is fecundated. 



To account for these facts, several authors 

 have supposed that, in plants, fecundation may, 

 in some circumstances, be effected without the 

 direct contact of the pollen with the stigma, and 

 merely through the influence of a kind of eman- 

 ation or aara polKnaris. But this question stiU 

 remains undecided. 



In the monoecious and dioecious plants, al- 

 though the two sexes are separated, and often 

 placed at a distance from each other, fecundation 

 is not on that account prevented from taking 

 place. In the case of dioecious plants, the pol- 

 len by which they are to he fecundated is trans- 

 ported often to great distances, by the air. 



When the stamens and pistils are situated near 

 each other, as in the case whether of hennaphro- 

 dite or monoecious flowers, the elastic spring with 

 which the anther flies open will generally be 

 sufficient to disperse the pollen, so as that part 

 of it must infallibly reach the stigma. The fa- 

 cilities tending to ensure the access of the pollen 

 as resulting from the relative proportion, situa- 

 tion, and mutual sympathies of the stamens and 

 pistils, have been already noticed ; as well as the 

 possible action of winds wafting the pollen to a 

 distance, and hence including the case of dioe- 

 cious plants also. But with all the above facili- 

 ties the impregnation of the seed would still, in 

 many cases, be impracticable even in hennaphro- 

 dite flowers, without further aid ; particularly 

 in such as do not perfect their stamens and 

 pistils at the same time. For although the 

 action of the wind cannot but be efficacious in 

 some such cases; yet it will, in some others, 

 naturall}' give to the flower a direction calculated 

 r.ither to prevent than to aid the access of the 

 pyllen, by causing the corolla to veer round like 



a vane according to the quarter from wliich it 

 may happen to blow ; or the very figure of the 

 corolla may operate as a bar to the entrance of 

 the pollen, which must be surmounted by ex- 

 traordinary means. 



What then are the means instituted by nature 

 for effecting the impregnation of hermaphrodites 

 so circumstanced? Tlie true reply to this in- 

 quiry seems to have been first suggested by 

 Koiilreuter, namely, the agency of insects ; and 

 has been since confirmed by the more leisurely 

 observations of Spregnel, who found that the 

 pollen in the above case is very generally con- 

 veyed from the anther to the stigma through 

 the instrumentality of bees, though sometimes 

 through that of insects of other species. The 

 object of the insect is the discovery of honey, 

 in quest of which, whilst it roves from flower 

 to flower and rummages the recesses of the 

 corolla, it unintentionally covers its body with 

 pollen, which it conveys to the next flower 

 it visits, and brushes off as it acquired it by 

 rummagingfor honey ; so that part of it is almost 

 unavoidably deposited on the stigma, and im- 

 pregnation thus eft'octed. Nor is this altogether 

 so much a work of random as it at first appeal's. 

 For it has been observed that even insects, which 

 do not upon the whole confine themselves to one 

 species of flower, will yet very often remain 

 during the whole day upon the species they 

 happen fiist to alight on in the morning. And 

 their agency is also completely secured, from 

 the necessity they are under of procuring food ; 

 though nature in her care for the impregnation 

 of the vegetable has not only lodged a honey in 

 the flower to tempt the taste of insects, but 

 seems to have furnished also the means of at- 

 tracting even the eye. This is thought to be 

 done by means of the coloured spots with which 

 many flowers secreting a honied fluid are marked, 

 as indicating the treasure that is contained in 

 the flower, and thus attracting the attention of 

 the insect. But the very figure of the flower 

 seems often intended to produce the same effect. 

 Spregnel has enumerated several hundreds of 

 flowers which in their figure as well as colour 

 resemble insects, and hence attract the notice of 

 the plunderers of their honied stores. The 

 beautiful example of the bee orchis is known to 

 almost every bodj-. 



Such then are the means by which the notice 

 of the insect is attracted ; and such also is the 

 structure of the internal parts of the flower, 

 that it must of necessity pass across the stamens 

 and pistils in procuring the honey it is in quest 

 of, which passage is often a work of considerable 

 difficulty, particularly when the tubular part of 

 the corolla is beset with hairs, as in many flowers 

 of the class pentan'lria and didt/namia. But 

 one of the most difficult and singular cases of 

 hermaphrodite impregnation, as aided by the 



