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EDINBURGH JOURNAL OF NATURAL HISTORY. 



tain this curvature. If these semiflorets thus curved outwards are transferred to syrup, 

 they curve in the opposite direction ; and if replaced in pure water, resume the outward 

 curvature. Thus, there is no doubt that all this is owinjT to endosmosp. If we allow 

 the semiflorets which are in the state of waking to remain some hours in aerated water, 

 they assume the incurvation which is that of sleep, and this incurvation is not destroyed 

 by transporting the semiflorets thus curved into syrup, which proves that this incurva- 

 tion of sleep is not owing to endosraose. As this incurvation of sleep does not take 

 place in unaerated water, this proves that it is owing to oxygenation. Thus the wake 

 and sleep of the semiflorets of the flower of the Dandelion result from the alternately 

 predominant incurvation of an orj^anic tissue incurvable by endosmose, and of an or- 

 ganic tissue incurvable by oxygenation. The first is undoubtedly the cellular tissue, 

 and the second the fibrous tissue, both contained in the nerves of the semifloret. These 

 two incurvable tissues, alternately prevailing the one over the other, open or close the 

 flower. 



The causes which effect the prevalence of the morning incurvation of the cellular 

 tissue, the agent of the state of waking, are, on the one hand, a more powerful ascent 

 of the sap under the influence of light, which increases the turgescence of that tissue, 

 and, on the other hand, the diminution of the antagonist force of incurvation of the 

 fibrous tissue, the agent of sleep, and w^hich takes place during the night. In fact, 

 if the semiflorets be gathered in the evening, when they have assumed the curvature 

 of sleep, and immersed in aerated water, they there retain without change their curve; 

 but if there be taken nest morning from the same flower, other semiflorets still retain- 

 ing the curvature of sleep, and they be immersed in aerated water, they instantly resume 

 the opposite incurvation, even in the dark. Now, by the immersion of the semiflorets 

 in water, endosmose of their cellular tissue is excited, and in consequence the curvature 

 of sleep is produced. If this result has not taken place in the evening, it is because 

 the incurvation by oxygenation of the antagonist fibrous tissue is too strong, and can- 

 not be overcome by the incurvation of the cellular tissue. If nest morning, by im- 

 mersing in water the semiflorets which have passed the night on the plant, their cur- 

 vature of sleep be produced, this proves that the force of incurvation of the fibrous 

 tissue has diminished, and that in consequence this fibrous tissue has lost a part of its 

 oxygenation during the night ; so that the cellular tissue incurvable by endosmosis, 

 which is its antagonist, and which is the agent of the state of waking, then prevails. 



Thus the flower, which for several days presents the alternations of waking and sleep, 

 is that in which the fibrous tissue, the agent of sleep, loses during the night a part of 

 the oxygen which has been fixed in its interior during the day, and which is the cause 

 of its incurvation ; so that the latter having in the morning lost some of its power, the 

 cellular tissue by endosmose, the agent of the state of waking, becomes again predo- 

 minant. The sleep of this flower takes place again in the evening, because the oxy- 

 genation of the fibrous tissue, the agent of sleep, gradually increases during the day, 

 which renders its incurvation predominant; at the same time the diminution of light 

 occasions the diminution of the sap, which weakens the turgescence, and consequently 

 the incurvation of the cellular tissue, the agent of waking. These alternations cease 

 only on the death of the corolla. The flowers which present only a single wake and 

 a single sleep, are those of which the single sleep is immediately followed by the death 

 of the corolla. 



The entire flower of the Dandelion immersed in its expanded state in unaerated wa- 

 ter, deprived of communication with the atmosphere, unchangingly retains this state 

 of waking. If the water is in contact with the atmosphere, it dissolves a portion of 

 the latter, and the flower which is immersed assumes the state of sleep at the end of 

 two or three hours. 



It may be remarked, that these experiments confirm what I have said in my paper 

 on the Respiration of Plants, namely, that vegetables respire like animals, by assimi- 

 lating oxygen, the presence of which in the organism is as necessary in the one as in 

 the other set of beings. 



MISCELLANEOUS. 



ON VARIETIES. NO. III. 



(^Continued from Page 120.) 



Varieties in colour are attributable to much the same causes as those producing 

 variations in size. This, however, is a subject more difficult of investigation, so little 

 being known of the modus operandi of these causes, and of the laws which regulate 

 their influence. Observations also are not likely to disclose much to us. Some per- 

 sons may be content with an explanation of this kind of varieties, derived from the idea 

 of nature ordaining them as so many additions to the beautiful variations every where 

 present in the universe ; but if we have recourse to such an explanation in the majo- 

 rity of cases, in the absence of immediate causes, there are instances which, plamly 

 contributing to the welfare of the object, or being, evince a benevolent design in the 

 Creator. Such an instance is seen in the common Trout, which, according to the 

 observation of anglers, conforms in colour to that of the river in which it is found, 

 that is, to the tint of the water or of its bed. It is also seen that plants, and other 

 stationary productions, are influenced in their colour by local circumstances. The 

 brilhancy of their colours is deteriorated or>destroyed, according to the degree of ob- 

 struction offered by surrounding bodies to the rays of the sun. Soil likewise affects 

 the colour of plants, though in a mode entirely unknown to us. Some localities pro- 

 duce certain coloured varieties of a given species of plant, and it is very probable that 

 many " accidental" varieties are attributable to the same cause. 



Food is thought in some cases to produce varieties in certain animals, and this is 

 not improbable in the case of such as are found scattered and exposed to differences 

 in the kinds of nourishment appointed for them. Among the facts available in sup- 

 port of the idea of variety in colour being an ordination of nature to increase the 

 beauty and interest of a species, it may be urged that a given colour is always liable 

 to give rise to modifications of the same in all its gradations, and these both as perma- 

 nent and accidental varieties ; but then there is onejjrule among plants which seems to 

 place the question on a diff"erpnt footing, namely, that all blue flowers are prone to 

 produce white varieties, that is, varieties destitute of colouring matter. In cases 



where two, three, or more colours appear together, and are diffused in patches over 

 the individual, we sometimes find no regularity adopted as to the size of such patches 

 or spots, or their figure, or relative position. Now, these are irregularities with the 

 causes of which we are not likely to become acquainted. The great tendency to va- 

 riation in colour of animals and plants is abundantly exemplified in domesticated and 

 cultivated species. 



As the causes that operate in producing varieties in size and colour are so obscure, 

 it cannot be surprising that an investigation of the same kind relative to varieties 

 affecting still more decidedly the species, and inducing differences in structure appre- 

 ciable for the most part by the naked eye, should be equally unsatisfactory in results. 

 Indeed, if the peculiarities distinguishing species cannot be satisfactorily explained m 

 the majority of cases, by reference to causes presumed to be in operation, those which 

 distinguish varieties must be also in the same predicament. The hairs and prickles of 

 plants are a kind of structure very prone to variation, and it seems that they increase 

 in number in dry situations, and diminish in such as are wet. But instances in which 

 causes can be traced are extremely rare, and little else can be done than to enumerate 

 varieties of this description. In many such we can discover without difficulty that 

 although varieties are in themselves departures from natural structure, they are 

 nevertheless produced under the influence or guidance of a law of formation. Thus, 

 in the case of Julus indicus, the additional members are produced by pairs, it bein" 

 in contradiction to suppose that a single leg could be formed by vessels, or the secret- 

 ing organs, which had previously formed two members at a time, the disposition or 

 arrangement of these secreting vessels being such that two structures instead of one 

 must as it were necessarily ensue. So, in the production of the parts of plants, if the 

 usual mode is by pairs, triplets, &c., the varieties will display the same arrano-ement. 

 Yet this rule is by no means invariably abided by. 



In addition to the forms of variety yet noticed, there are ^)ther3 which it is neces- 

 sary to enumerate, though their causes are quite inappreciable. Plants usually odori- 

 ferous are liable to become scentless under certain circumstances, and it is thought 

 that the rays of the sun are in some cases essential to the production of this quality. 

 Scent is of course dependant on the presence or condition of some structure, and it 

 would therefore be requisite to inquire what this structure is in each case, and what 

 circumstances are liable to vary its formation and its qualities. The taste or flavor 

 also, both of animals and plants, is liable to slight diff'erences, dependant most probablv 

 on soil, situation, and food. The Oyster, for instance, varies, in taste according to 

 the river from whicli it has been procured. The Salmon, the Trout, and the Perch 

 also differ in this respect. Peppermint varies in flavor according as the soil suits its 

 constitution, and the same is well known to be the case with regard to Grapes, Melons, 

 and many other kinds of fruit. 



The song and notes of birds, especially of those which are not confined to a mono- 

 tonous song, or to one particular key, is in some instances not a little different from 

 that proper to the species. Besides, minor differences are frequently observed in in- 

 dividuals. On this subject see some remarks in the " Journal of a Naturalist." The 

 habits or actions of animals, too, exhibit some individual peculiarities of the same 

 amount, there remaining, however, those distinguishing features which serve to char- 

 acterize the animal, and separate it from every other. In short, all that I contend 

 for is this : — That, as there exist between species certain differences of a greater or 

 less extent, by which they are respectively known and characterized ; so there exist 

 between the individuals of a species diffeiences of a greater or less degree forming a 

 line of demarcation, or peculiarities characterizing and separating one from another. 

 To my apprehension, nature has been desirous of fixing these bounds, and impressing 

 on individual productions marks which cannot be effaced, thereby preservin<r the same 

 rule as regards the component parts of species, as is noticed between the specific com- 

 ponents of the organic world. These last-named varieties are well seen in domestic 

 animals, and in cultivated specimens of plants, though I by no means appeal to these 

 in support of my opinion. 



Much of the difl[iculty attnched to an inquiry as to the uses of varieties would be 

 banished by admitting that, besides nature appointing a certain series of differences be- 

 tween individuals of a species, she has also in very many cases appointed uses, separate 

 or additional, for varieties occurring to species. Unless we admit that some particular 

 oflSce, or function, is set apart for very many varieties we meet with, I do not see how 

 we are to account for their differences being so great. I conceive that in many in- 

 stances, not only are the amounts of difference .assumed as varieties, as great as those 

 between species, but that their uses are as peculiai-ly important in the oreat scheme of 

 the universe, as those of a vast number of species belonging to the same class or tribe 

 as the varieties. It is not pretended, however, that these uses can be defined, and it 

 is but an inference to say varieties execute functions different from ordinary specimens. 

 In the case of animals and plants which we employ as food, or for economical pur- 

 poses, we are led to the conviction that here varieties are indispensable, because al- 

 though some maintain existence under unaltered forms when dispersed over a lar-re 

 extent of country, and exposed to great diversity of circumstances, surroundino- media, 

 and conditions are ever differing, and the surface of the earth is composeil of hetero- 

 geneous materials, different kinds of soil being frequently found in adjacencv within verv 

 confined limits, and consequently the occurrence of such species would be very circum- 

 scribed, unless by the means of variation they could adapt themselves to such diversi- 

 fications. In the vegetable world we may instance wheat, barley, maize, other kinds 

 of grain, and various species of grass. Now, if these did not conform to the different 

 soils, man would be debarred from participating in the benefits they confer, excepting- 

 in those particular localities whichh appened to agree with them. And so, if certain 

 heights were ordained for trees, they could only be found in those soils and situations 

 which allowed them to attain those heights. — To be continued. 



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