Pagina-afbeeldingen
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their ideas of fimilitude. When Rivinus informs us that enchanter's night-fhade has two regular petals, ladies fmock four, St. John's wort five, tulip fix, and anemony many, every one who knows the part in queftion, and has learned to diftinguish, in dubious cafes, betwixt flowers of one petal, and flowers of more petals than one, must enter immediately into the Author's meaning, and be thence enabled to refer each plant to its refpective clafs or divifion. Let us make a fimilar experiment in cafe of figure, and attend the iffue. That bind-weed, bell-flower, deadly night-fhade, and the numerous plants of the mallow and cucumber tribes, fhould be made to arrange themselves under a clafs containing bell-shaped flowers, can appear strange to no one who knows ever fo little of the plants that have been mentioned. The refemblance is obvious and ftriking; and it is next to impoffible that a learner who has been previously instructed in the principles and analyfis of Tournefort's method, fhould miftake in making the proper reference to his arrangement. A particular clafs, he is informed, the Author has allotted for the reception of plants with bell-shaped flowers: gentian, melon, and the plants juft enumerated, have manifeftly flowers of that defcription; their place, therefore, in the arrangement, cannot be matter of difquifition or doubt for a moment; it is immediately afcertained. But there are inftances in which the determination of the class or primary divifion, is not a point of fuch extreme facility. Who, for example, would look for crosswort, ladies bed ftraw, cleavers, madder, and rhubarb, among the bell-shaped flowers? or expect to find loofe-ftrife, pimpernell, fpeedwell, and borrage conjoined with flowers which in fhape refemble a funnel? Yet thefe falfe arrangements, incredible as it may appear, are chargeable upon the method adopted by Tournefort, as are likewife many others of the fame kind,'

Our botanist had hitherto fuppofed the conftancy of the rival principles, number and figure, to be equal: he now proceeds, after other obfervations, to enquire and determine with accuracy, in favour of which diftinction so capital a circumftance declares itself. He produces many examples of variations in refpect to the firft, and then remarks, that in fome of the inftances mentioned of occafional variations in point of number, changes little lefs remarkable or confpicuous are effected in the general fymmetry and figure of the parts. After this he alfo mentions fome of the moft confiderable of thofe accidental alterations in the figure of the feveral parts of plants which are totally unconnected with casual variations of number, and unaffected by them.

The refult of thefe difquifitions is given us in the two following, and, as our Author fays, evident, confequences: the one, that figure, in general, is not a more infallible diftinction than

number.

number. The other, that more frequent variations are exhibited by the petals in point of number, than of figure. On the whole, therefore, we fhould have concluded that Tournefort's method of arrangement was preferable to that of Rivinus. But this Writer appears with juftice to remark, Had Tournefort, in adopting the figure of the petals for his primary diftinction, preferved it totally unconnected with every other, he would thereby have imparted to his method a degree of excellence abfolutely unattainable by that of Rivinus, from the greater inconftancy of its principle or leading character. Far, however, from availing himfelf as he ought, of fo diftinguished an advantage, the French botanift has overlooked it altogether, and, by combining number with figure, and even postponing the latter to the former, has introduced into his method the inconveniences of either diftinction, and thus rendered the execution of his plan more exceptionable than that of his predeceffor, and widely different from what would have refulted from a developement of the fame principle closely adhered to.'

Dr. Milne acknowledges Tournefort's method to have been justly celebrated, and is particular in illuftrating the general fcheme, Not only, he fays, out of refpect to the diftinguifhed character of its author, but because several of the claffes are properly its own, and poffefs a degree of facility, that could fcarce have been expected in a plan of arrangement, which feems to have propofed the inveftigation of natural families as the standard of excellence. Rivinus made choice of a principle which, being obferved with the moft fcrupulous exactness, had totally excluded every natural affemblage, whether of a primary or fecondary kind. It was Tournefort's intention, in adopting a principle that admits of greater latitude, to restore its imagined utility to the fcience; by re-establishing as far as the artificial character would permit, thofe natural claffes and genera, which Rivinus, preferring facility to every other advantage, had difmembered and fplit.'

As figure admits of much greater latitude than number, therefore, our Author obferves, the French botanist's method, however beautiful in the idea, is much more difficult in practice than that of his predeceffor, Rivinus, whofe fole object was to facilitate the knowledge of the plants. He particularizes the moft remarkable of the general diftinctions, (in the fecondary divifions in Tournefort's method) which are founded principally upon the fruit, as thofe of the claffes are upon the flower, and he accompanies his account of thefe diftinctions with explanatory obfervations: he alfo points out the principal errors, and difficulties attending this fchen:e: for a particular account of all which we must refer the Reader to the work itself, without adding any thing farther relative to what is faid upon this celeREV. Oct. 1772.

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brated method, than that the Doctor difmiffes it by presenting us with a lift of the moft confiderable writers by whom it has been adopted: the lift is numerous, but among them all Father Plumier, and Pontedera alone, have ventured to quit the track pointed out by Tournefort.

We now come to an account of methods founded upon the calix or flower cup; of which there are only two: the one invented by Peter Magnol, a celebrated profeffor of botany at Montpelier, and published in 1720, five years after the author's death the other delineated by Linnæus, and published in his claffes plantarum, in 1738, three years after the publication of the Sexual System: The former, fays our Author, is fingular in its kind, and acknowledges principles of diftribution, totally different from any that have hitherto been explained.' After a brief view of this particular mode of arrangement, it appears that, facility is by no means its characteristic. It is in fact, fays this Writer, of all others the most difficult in practice, nor do I know that it poffeffes a fingle quality, fave novelty alone, to recommend it. The obfervations with which it abounds, however ingenious, are frequently whimfical, and calculated to milead. The very foundation of Magnol's method is deceptive for, although it fets' out with the calix, and even profefies an uniform adherence to that part of fructification, in characterizing the claffes, the learner will not have advanced many fteps, before he finds himself bewildered in diftinctions from the fruit: diftinctions leaft of all to be expected, in a method founded profeffedly on the calix; yet attempted to be made compatible with the principles of fuch method, by the operation of an imagined connection and affinity between the calix and fruit.'

Notwithstanding this cenfure paffed upon the Magnolian method, Dr. Milne allows that there are many circumstances which, under proper reftrictions, render the calix no contemptible foundation of a botanical fyftem. Of all, or moft of thefe circumftances, he adds, has Linnæus availed himself in the conftruction of his Method founded upon the calix, which in the idea and execution, is greatly fuperior to that of Magnol; and is indeed fingularly ufeful, in familiarizing to the novice in botany, the various appearances of an organ fo important in its nature, and fo diverfified in form.'

The attention of the Reader is in the next place called to the Sexual Syflem, of which the fixth fection of this work contains the analyfis and examination: it is founded upon the number, proportion, fituation and union of the ftamina, chives, or flender threads of the flower; and proceeds upon a fancied analogy betwixt the feveral parts of plants and thofe of animals, fuppoling the existence and concourfe of the fexes to be as in

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difputably ascertained in the former as in the latter. The organs indifpenfibly neceffary to fructification are reduced to two, the ftamina and piftils; the neceffity of these is evinced by feveral obfervations from which it appears, fays this Writer, That there is no plant capable of furnishing good, wellconditioned feeds, that is not provided with ftamina and pittil. That flowers which poffefs the highest degree of luxuriance, and have all the ftamina metamorphofed into petals, produce no perfect feeds. That feeds equally barren and imperfect, are furnished by fuch flowers as have their piftil transformed into flender expanfions, refembling leaves. That if the ftamina of any plant are cut off before the anthera or fummits have difperfed the powder inclofed within their fubftance, the fruit is productive of imperfect feeds. That a fimilar abortion takes place, when, upon the expanfion of the flower, the style or ftigma (the fummit of the piftil) is cut off; when the moisture which covers that organ is totally abforbed by continual fmoke, or carried off by perpetual fhowers; when the tops of the ftamina are hindered from opening by fudden frofts, or their powder diluted or wafhed away by violent rains.' These facts prove that the ftamina and piftils are abfolutely neceffary towards the formation of the feeds.

The feeds of plants, proceeds our botanift, in another place, are true vegetable eggs: as fuch, they require to be fecundated, before they can be capable of producing a plant fimilar to the parent-plant. Vegetables then have the neceflary organs of the two fexes: but what are thefe organs and where do they refide?

It is evident that we must feek for the organs of generation in plants, in the parts where the feeds are formed, where they receive fecundation, and where they take their growth. Thofe parts are the flower and fruit; which are therefore very properly defined by Linnæus, the organs of generation of plants which ferve, the former, for the fecundation of the feeds, the latter for the nourishment of the fætus. Now all plants which bear feeds have ftamina and piftils. The ftamina are the male parts, the piftils the female. When the ftamina and pistils are found collected in the fame fructification, as happens in the greater number of plants, the flower is termed hermaphrodite. When the fructification contains ftamina only, the flower is termed male, when piftils only, female. Male and female flowers are fometimes. produced upon different parts of the fame individual plant, fometimes from different individuals fprung from the fame feed. The plants in the former cafe, are termed androgynous, in the latter, male and female.'

In fupport of this hypothefis of the existence of the fexes in plants, a variety of proofs are offered, fome of which are here mentioned: we hall felect only that which follows:

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M. Duhamel du Monceau, fays our Author, relates an experiment performed by himself and M. Bernard de Juffieu, a celebrated French academician, which bids fair to be decifive upon the queftion of the fexes. In the garden of M. de la Serre of the Rue S. Jaques at Paris, was a female turpentine tree, which flowered every year, without furnishing any fruit capable of vegetation. This was a fenfible mortification to the owner, who greatly defired to have the tree increased. Mefirs. Duhamel and Julicu very properly judged that they might procure him that pleasure with the affiftance of a male pistachio tree. They fent him one very much loaded with flowers. It was planted in the garden of M. de la Serre very near the female turpentine tree, which the fame year produced a great quantity of fruits, that were well-conditioned and role with facility. The male plant was then removed, the confequence of which was, that the turpentine tree of M. de la Serre in none of the fucceeding years bore any fruit, that, upon exami nation was found to germinate.'

We will here infert fome of thofe arguments which are drawn from the ftructure, proportion, fituation and other cir cumftances of the fexual organs, and which are thought farther to fupport the doctrine of vegetable fecundation.

The male duft, we are told, is difcharged by its proper organ, at the very time when the ftigma of the piftil is in its greatcft vigour, and confequently beft difpofed to receive the influences of the fecundating matter.-After the discharge of the pollen, or powder of the anthera (the fummits of the chives or ftamina) both ftamina and piftils wither and fall off.-The fituation of the pills with refpect to the ftamina appears favourable for the reception of the fecundating duft.-The greater part of aquatic plants flower only above the water, that the fecundation, as Gefner obferves, may be performed in air, and the generating fubftance may not be diluted by the water. Some plants it is remarkable, plunge again into the water, as foon as fecundation is accomplished, and the fruits begin to be formed. The figure of the pollen in plants of the fame fpecies is exactly fimilar; in thofe of different fpecies and genera, its figure is exceedingly diverfified. Hence we may conclude, with fome degree of probability, that the powder in queftion, being a compofition of organized capfules, is not a fimple excrement or fecretion, as fome naturalifts have pretended, but a viscus effentially neceffary to plants, and whofe function it is to per petuate the fpecies.'

The doctrine of the fexual difference in plants was not totally unknown to the ancients; they had particularly obferved it with regard to palm-trees. Several botanifis before the time of Lanaus had diftinguished plants into male and female, and

that,

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