O-t 



HISTORY OF THE VEGETABLE KINGDOM. 



different plants, do not all come to maturity pre- 

 cisely at the same time, the flower whose sta- 

 mens have fallen before the maturity of its pistil, 

 may still be impregnated by the pollen of an- 

 other flower or plant with which the period of 

 its maturity is identical, and to which it may 

 be ambiguous. And in this way we may believe 

 the impregnation of many flowers is effected, 

 particularly in the ease of the Indian corn, the 

 barren flowers of which, upon the same plants, 

 have generally quite decayed before the fertile 

 flowers have burst fi-om the bosom of the leaves, 

 at least as it grows in this country, as also in 

 the case of the jatropha urcns, the barren flowers 

 of which are generally protruded either several 

 weeks sooner or several weeks later than the 

 fertile flowers, and are consequently either de- 

 cayed or not yet come to maturity at the time 

 the style is perfect. But if the fertile flower 

 should not be contiguous to the ban-en flower, 

 the pollen may yet be wafted to it by means of 

 the wind, which curious phenomenon may some- 

 times be distincalyseen. On the ]4th June, 1808, 

 says Dr Keith, as I was accidentally looking at 

 a field of rye grass situated to the south of the 

 spot on which I then stood, the atmosjihere 

 being clear, and the wind blowing gently from 

 the west, I was surprised to observe a thin and 

 sudden cloud, as if of smoke, a fine dust, sweeping 

 briskly along the surface of the grass, and gradu- 

 ally disappearing. This cloud was soon followed 

 by a second from a different quarter of the field, 

 and that by a tliird, and so on in succession for 

 several minutes. It was a general discharge of 

 pollen from thousands of anthers bursting at the 

 same moment, so that no stigma ready to receive 

 the pollen could possibly fail of being supplied, 

 either fi-om the anthers proper to the flower of 

 which it formed a part, or ii-om those of some 

 other flower discharging their contents into the 

 general mass. The distance to which the pollen 

 may be conveyed on a short exposure to the 

 action of a fine atmosphere, is not likely to do 

 it any damage. Linnsus kept some of the 

 pollen of the jatropha urcns in paper for more 

 than a month, which even after that period 

 fertilised the pistils over ^^'hich it was shaken. 

 Such were the doubts entertained by the scepti- 

 cal prior to the elucidations of Linnseus, and 

 indeed they arose almost naturally out of the 

 darkness in which the subject was then involved. 

 But as the elucidationsof Linnaeus, though capa- 

 ble of affording con-riction to the minds of the 

 impartial inquirer, were not able to subdue 

 passions, or to eradicate prejudices imbibed by 

 education, or excited by compassion, the doc- 

 trine of the sexes of vegetables met also with 

 many opponents even in the time of Linnseus. 

 Tlie most zealous of them was Dr Alston of 

 Edinburgh, who professing to be dissatisfied with 

 every thing that had been said or done in sup- 



port of the doctrine, made a show of refutirg 

 it by means of counter experiments, of which 

 the most foi-midable are the following. Admitt- 

 ing the result of the experiment of the cutting 

 oft' of the anthers before the ripening of tho 

 poUen, to be what Linnseus and others affirm 

 the abortion of the seed, he will not allow that 

 it authorises any conclusion in favour of the 

 sexes of plants, because he thinks it is to be 

 expected that a wound in any essential part of 

 the plant, together with consequent loss of juice 

 issuing from it, will occasion abortion in the 

 seeds, and in confirmation of this presumption, 

 he quotes an experiment of Malpighi, who found 

 that the ripening of the seeds of a tulip was pre- 

 vented by means of the putting off the petals 

 before their expansion. But the two experi- 

 ments are not at all of the same kind. In tho 

 latter, there was a material injury done to tho 

 flower in consequence of its being prematurely 

 stripped of the covering of the corolla ; in the 

 former there was no material injury done to 

 the flower, because the anthers were not cut off 

 till after the natural expansion of the petals, in 

 which case it is very well known that if the 

 pistil is impregnated even with the pollen of 

 another flower, the seeds will still ripen. But 

 Alston does not even admit the i'act that the 

 stripping of a plant of its stamens, will render 

 the seed abortive. Alleging in support of his 

 opinion Geofii-ey's experiments on maze, in 

 which it was found that some of the ears 

 ripened a few seeds even when the stamens were 

 entirely cut ofi^ before the bursting of the an- 

 thers, together with a similar experiment of his 

 own upon a solitary tulip, by which the ovary 

 suffered nothing, but increased, and came to 

 maturity quite full of seeds. Now the defect of 

 the argument is, that we are not told whether 

 the seeds were put to the proper test, that is, 

 whether they were sown, and found capable of 

 germination. The next counter experiment was 

 made upon ditecious plants. Three plants of 

 common spinach, which were removed before it 

 could be told whether they were to be fertile or 

 barren, to a distance of at least eighty yards 

 from the bed in which they were raised, and 

 from which also they were separated by several 

 intervening hedges, proved in the end to be all 

 fertile, and ripened plenty of seeds that germin- 

 ated again when sown. A solitary plant of 

 hemp also, that sprung up in Dr Alston's garden, 

 having no other plant of the species within a 

 mile of it to his knowledge, grew luxuriantly, and 

 produced seeds that germinated also when sown. 

 These experiments are contradictory no doubt, 

 to the experiments of Linnaeus, but they afford 

 no argument against the doctrine of the sexes. 

 For in the first place, it cannot be proved that 

 some of the pollen from the spinach bed, or 

 fi-om a neiglibouring male plant of hemp, might 



