82 



HISTOaY OP THE VEGETABLE KINGDOM. 



the perfect expansion of the flower ; but, in the 

 greatest number of vegetables, this phenomenon 

 does not happen until after the floral envelopes 

 have opened and spread out. In certain herma- 

 phrodite flowers, the length or shortness of the 

 stamina, compared with the pistil, might at first 

 seem to present an obstacle to fecundation ; but, 

 as already remarked, when the stamina are 

 longer than the pistil, the flowers are generally 

 erect, whereas in those which have the stamina 

 shorter than the pistil, they are reversed. We 

 need not point out how much this arrangement 

 must facilitate the act of fecundation. When 

 the stamina are as long as the pistils, the flowers 

 are either erect or pendulous. 



To favour the emission of the poUen, and 

 place it in contact with the stigma, the sexual 

 organs of many plants perform very sensible 

 motions. Thus, to recur to examples already 

 alluded to, at the period of fecundation, the 

 eight or ten stamina which compose the flowers 

 of the rue rise successively towards the stigma, 

 deposit part of their pollen upon it, and then 

 fi'.U outwards. 



The stamina of sparmannia Africana and the 

 barberry when irritated with the point of a 

 needle, contract and approach each other. 



In several genera of the family of Urticese, in 

 the pellitory and the paper mulberry, the stamina 

 are bent towards the centre of the flower, and 

 beneath the stigma. At a certain period, they 

 rise elastically, like so many springs, and cast 

 their pollen upon the female organ. 



In the genus Kalmia, the ten stamina are 

 placed horizontally at the bottom of the flower, 

 and their anthers are enclosed in an equal number 

 of small pits, which are perceived at the base of 

 the corolla. To produce fecundation, each of 

 the stamina bends a little upon itself, in order 

 to disengage its anther from the little cavity 

 wliich contains it. It then rises above the pistil, 

 and pours its pollen upon it. 



The female organs of certain plants appear in 

 like manner to perform motions which depend 

 upon their greater irritability during the period 

 of fecundation. Thus the stigma of the tulip, 

 and several other hliaceae, swells and appears 

 raolster at that time. The two laminae which 

 fomi the stigma of the mimulus come together 

 whenever a little mass of pollen, or a foreign 

 body of any kind, happens to touch them. It 

 even appears, according to the observations of 

 Lamarck and Bory St Vincent, that some plants 

 develope a very sensible heat at this period. 

 Thus, in arum Italicum, and some other plants 

 of the same family, the spadix which sup- 

 ports the flowers disengages a quantity of heat 

 sufficient to be felt by the hand that touches 

 it. 



Many aquatic plants have their flower buds 

 at first under water. They are seen gradually 



to approach the surface, emerge, and expand, to 

 descend again after fecundation has taken place, 

 and ripen their seeds under the water. 



Fecundation may be effected, however, in 

 plants that are entirely submersed. Thus, Ea- 

 mond found, in the bottom of a lake among the 

 Pyrenees, the ranunculus aquatilis covered with 

 water to the height of several feet, and yet bear-, 

 ing flowers and perfectly ripe fraits. Fecunda- 

 tion had therefore been effected in the midst of 

 the liquid. M. Batard afterwards found the 

 same plant in similar circumstances. He made 

 the curious remark that each flower, thus sub- 

 mersed, contained a quantity of air within its 

 membranes, previous to its expansion, and that 

 fecundation was effected through the medium 

 of that fluid. The air which he thus found en- 

 closed in the floral envelopes was evidently de- 

 rived from vegetable expiration. 



This observation, the accuracy of which has 

 since been repeatedly verified, explains perfectly 

 the mode in which submersed plants are fecun- 

 dated, when they are famished with floral en- 

 velopes ; but it is totally inapplicable to vegeta- 

 bles destitute of the calyx and corolla, the fecun- 

 dation of which is effected, altho\igh their flowers 

 are entirely submersed. 



But admitting that the pollen is conveyed to 

 the stigma by the means above stated, how is it 

 thence conducted to the ovary? It was at one 

 time generally supposed that the pollen is con- 

 ducted from the stigma to the ovary by means 

 of a longitudinal canal perforating the style. 

 This canal is distinguishable in many of the 

 liliaceous plants, in which it seems indeed to 

 constitute the passage of the poUen, particularly 

 from the phenomenon of the amaryllis formos- 

 issima, the fluid exuding from the stigma of 

 which returns again through the perforation of 

 the style tinged with yellow, the colour of the 

 pollen. But the existence of the canal in ques- 

 tion, though distinguishable in the amart/llts 

 formosissima, and other lUiaceous plants, cannot 

 be admitted as a universal property of the style, 

 at least it cannot be detected. And if it is so 

 very fine as to escape all observation, then it 

 could not admit the particles of poUen, which are 

 in some cases comparatively large, as in marvel 

 of Peru ; the poUen of which exceeds the style 

 itself in diameter, and could not consequently 

 be admitted by a central canal. 



But in order to efifect the impregnation of the 

 seed it is not necessary that the particles of pol- 

 len should enter the style entire. The finer 

 part of their contents is sufficient, and is indeed 

 the only effective part in the act of fecundation : 

 so that whether we regard it as a subtle and 

 elastic vapour with Grew and Adanson; or 

 merely as an oily and gelatinous fluid exuding 

 or exploding from the globule ; still it wai ad- 

 mit of beuig conducted through the chaimel of 



