Book I. 



SEXUALITY OF VEGETABLES. 



249 



two or more koines, although it rarely happens that more than one is developed. But if two apples or 

 pears are developed in an incorporated state, which is a case that now and 

 then occurs, it is no doubt best accounted for by the graft of Du Hamel. 

 Sometimes the anomally consist in the figure of the fruit, which is del 

 formed by tumours or excrescences, in consequence of the bite of insects 

 or mjuries of weather producing warts, moles, or specks. Sometimes it 

 consists in the colour, producing green melons and white cucumbers. 

 Sometimes it consists in an appendage of leaves, [fig. 195.) 



1618. Habit. The anomalies of habit are principally oc- 

 casioned by soil and cultivation. 



1()19. Some plants, which, when placed in a rich soil, grow to a great 

 height, and affect the habit of a tree, are, when placed in a poor soil, 

 converted into dwarfish shrubs. This may be exemplified in the case of 

 the box-tree ; it also occurs in the case of herbaceous plants ; as in that 

 of Myosbtis, which in dry situations is but short and dwarfish, while in 

 moist situations it grows to such a size as to seem to be altogether a differ- 

 ent plant. The habit of the plant is sometimes totally altered by means 

 of cultivation : the Pyrus satlva, when growing in a wild and unculti- 

 vated state, is furnished with strong thorns ; but when transferred to a 

 rich and cultivated soil the thorns disa|)pear. This phenomenon, which 

 was observed by Linnaeus, was regarded as being equivalent to the taming of animals : but this explica- 

 tion is, like some others of the same great botanist, much more plausible than profound, in place of winch 

 Professor Willdenow substitutes the following ; the thorns protruded in the uncultivated state of the plant, 

 are buds rendered abortive from want of nourishment, which when supplied with a suflSciency of nourish, 

 ment are converted into leaves and branches. 



1 620. P/iJ/sical virtues. When plants are removed from their native soil and taken 

 into a state of culture, it alters not only their habit but their physical virtues. Thus the 

 sour grape is rendered sweet ; the bitter pear, pleasant ; the dry apricot, pulpy ; the prickly 

 lettuce, smooth ; and the acrid celery, wholesome. Potherbs also are rendered more tender, 

 by means of cultivation, and better fitted for the use of man ; and so are all our fine fruits. 



1621. Duration. Plants are either annuals, biennials, or perennials, and the species 

 is generally of the same duration in every climate. But it has been found that some 

 plants, which are annuals in a cold climate, such as that of Sweden, will become peren- 

 nials in a hot climate, such as that of the West Indies ; this anomaly has been exemplified 

 in Tropce^olum, beet root and il/Alva arborea : and, on the contrary, some plants, which 

 are perennials in hot climates, are reduced to annuals when transplanted into a told 

 climate ; this has been exemplified in the climbing kidneybeans. 



Sect. VI. Of the Sexuality of Vegetables. 



1622. The doctrine that plants are of different sexes, and which constitutes the found- 

 ation of the Linnean system, though but lately established upon the basis of logical in- 

 duction, is by no means a novel doctrine. It appears to have been entertained even 

 among the original Greeks, from the antiquity of their mode of cultivating figs and palms. 

 Aristotle and Theophrastus maintained the doctrine of the sexuality of vegetables ; 

 and Pliny, Dioscorides, and Galen adopted the division by which plants were then dis- 

 tributed into male and female ; but chiefly upon the erroneous principle of habit or 

 aspect, and without any reference to a distinction absolutely sexual. Pliny seems to 

 admit the distinction of sex in all plants whatever, and quotes the case of a palm tree as 

 exhibiting the most striking example. 



lG-2o. Linnceus, reviewing with his usual sagacity the evidence on which the doctnne rested, and per- 

 ceiving that it was supported by a multiplicity of the most incontrovertible facts, resolved to devote his 

 labours peculiarly to the investigation of the subject, and to prosecute his enquiries throughout the whole 

 extent of the vegetable kingdom ; which great and arduous enterprise he not only undertook, but accom- 

 phshed with a success equal to the unexampled industry with which he pursued it. So that by collecting 

 into one body all the evidence of former discovery or experiment, and by adding much that was original of 

 his own, he found himself at length authorised to draw the important conclusion, that no seed is perfected 

 without the previous agency of the pollen, and that the doctrine of the sexes of plants is consequently 

 founded in fact. 



1624. Proofs from the economy of the aquatics. Many 

 plants of this class which vegetate for the most part wholly 

 immersed in water, and often at a considerable depth, 

 gradually begin to elevate their stems as the season of 

 flowering advances, when they at last rear their heads 

 above the surface of the water, and present their opening 

 blossoms to the sun, till the petals have begun to fade, after 

 which they again gradually sink down to the bottom to 

 ripen and to sow their seeds. This very peculiar economy 

 may be exemplified in the case of .fl(appia maritima, and 

 several species of Potamog^ton common in our ponds 

 and ditches. From this we may fairly infer, that the 

 flowers rise thus to the surface merely to give the pollen 

 an opportunity of reaching the stigma uninjured. But 

 the most remarkable example of this kind is the Val- 

 lisneria spiralis {fig 196.), a plant which grows in the 

 ditches of Italy. The plant is of the class Dioe'^cia, pro- 

 ducing its fertile flowers on the extremity of a long and 

 slender stalk (a) twisted spirally like a corkscrew, which 

 uncoiling of its own accord, about the time of the open- 

 ing of the blossom, elevates the flowers to the surface of 

 the water, and leaves them to expand in the open air. 

 The barren flowers (6) are produced in great numbers upon 

 short upright stalks issuing from a different root, from 

 which they detach themselves about the time of the 



