BLUE, caruleus.
GREEN.
These colours seem to be appropriated to particular parts of the plant. Thus, white is most common in roots, sweet berries, and the petals of spring flowers. Water-colour, in the filaments and styles. Black, in the roots and seeds; rarely in the feed-vessel, and scarce ever to be found in the petals. Yellow is frequent in the anther or tops of the stamens; as likewise in the petals of autumnal flowers, and the compound ligulated flowers of Linnaeus. Red is common in the petals of summer flowers, and in the acid fruits. Blue and violet-colour, in the petals. Green, in the leaves and calix, but rarely in the petals. In the interchanging of colours, which in plants is found to depend upon differences in heat, climate, soil and culture, a sort of elective attraction is observed to take place. Thus, red is more easily changed into white and blue; blue into white and yellow; yellow into white; and white into purple. A red colour is often changed into a white, in the flowers of heath, mother of thyme, betony, pink, viscous campion, cucubalus, trefoil, orchis, fox-glove, thistle, cudweed, saw-wort,
rose, poppy, fumitory, and geranium. Red passes into blue in pimpernel. Blue is changed into white in bell-flower, greek-valerian, bindweed, columbine, violet, vetch, milk-wort, goat's rue, viper's bugloss, comfrey, borrago, hyssop, dragon's-head, scabious, blue-bottle, and succory. Blue is changed into yellow in crocus. Yellow passes easily into white in melilot, agrimony, mullein, tulip, blattaria, or moth-mullein, and corn marigold. White is changed into purple in wood-forrel, thorn-apple, pease, and daisy.
Although plants are sometimes observed to change their colour upon being moistened with coloured juices, yet that quality in vegetables seems not so much owing to the nature of their nourishment, as to the action of the internal and external air, heat, light, and the primitive organisation of the parts. In support of this opinion, we may observe with Dr Grew, that there is a far less variety in the colours of roots than of the other parts of the plant, the pulp, within the skin, being usually white, sometimes yellow, rarely red. That this effect is produced by their small intercourse with the external air appears from this circumstance, that the upper parts of roots, when they happen to stand naked above the ground, are often dyed with several colours: thus the tops of forrel roots turn red; those of turnips, mullein, and radishes, purple; and many others green: whilst those parts of the same roots which lie more under ground are commonly white. The green colour is so proper to leaves, that many, as thole of fage, the young sprouts of St John's wort, and others which are reddish when in the bud, acquire a perfect green upon being fully expanded. In like manner, the leaves of the sea-side grape, polygonum, which when young are entirely red, become, as they advance in growth, perfectly green, except the middle and transverse ribs, which retain their former colour.
As flowers gradually open and are exposed to the air, they throw off their old colour, and acquire a new one. In fact, no flower has its proper colour till it is fully expanded. Thus the purple stock-julyflowers are white, or pale in the bud. In like manner bachelor's buttons, blue-bottle, poppy, red daisies, and many other flowers, though of divers colours when blown, are all white in the bud. Nay, many flowers change their colours thrice successively; thus, the very young buds of lady's looking-glass, bugloss, and the like, are all white; the larger buds purple, or murrey; and the open flowers blue.
With respect to the colours of the juices of plants, we may observe, that most resinous gums are tinctured; some, however, are limpid; that which drops from the domestic pine is clear as rock-water. The milk of some plants is pale, as in burdock; of others white, as in dandelion, euphorbium, and scorzonera; and of others yellow, as in lovage, and greater celandine. Most mucilages have little colour, taste or smell. Of all the colours above enumerated, green is the most common to plants, black the most rare.
Colour being a quality in plants so apt to change, ought never to be employed in distinguishing their species. These ought to be characterised from circumstances not liable to alteration by culture or other accidents. The same inconsistency of colour observed in
Colour. in the flowers, is likewise to be found in the other parts of plants. Berries frequently change from green to red, and from red to white. Even in ripe fruits, the colour, whether white, red, or blue, is apt to vary; particularly in apple, pear, plum, and cherry trees. Seeds are more constant in point of colour than the vessel which contains them. In the seeds, however, of the poppy, oats, pea, bean, and kidney-bean, variations are frequently observed. The root too, although not remarkably subject to change, is found to vary in some species of carrot and radish. Leaves frequently become spotted, as in a species of orchis, hawk-weed, ranunculus, knot-grass, and lettuce; but seldom relinquish their green colour altogether. Those of some species of amaranthus, or flower-gentle, are beautifully coloured. The spots that appear on the surface of the leaves are of different colours, liable to vary, and not seldom disappear altogether. The leaves of officinal lung-wort, and some species of sowbread, forrel, trefoil, and ranunculus, are covered with white spots. Those of dog's-tooth violet, with purple and white. Those of several species of ranunculus, and orchis, and a kind of knot-grass called by Tournefort persicaria ferrugine quinum referens, with black and purple. Those of amaranthus, tricolor, with green, red and yellow. Those of ranunculus acris, and a species of bog-bean, with red or purple. The under surface of the leaves of some species of pimpernel and the sea-plantain is marked with a number of dots or points; a white line runs through the leaves of Indian reed, black-berried heath, and a species of canary grass: and the margin or brim of the leaf, in some species of box, honey-suckle, ground-ivy, and the ever-green oak, is of a silver-white colour. The whole plant is often found to assume a colour that is unnatural or foreign to it. The varieties in some species of eryngo, mugwort, orrach, amaranthus, purslane, and lettuce, furnish examples.
Such being the inconstancy of colour in all the parts of the plant, specific names derived from that quality are, very properly, by Linnæus, deemed erroneous; whether they respect the colour of the flower, fruit, seeds, root, leaves, or express in general the beauty or deformity of the entire plant, with a particular view to that circumstance. Of this impropriety committed by former botanists, Linnæus himself is not always guiltless. Thus the two species of sarracena, or the side-saddle flower, are distinguished by the colour of their petals into the yellow and purple sarracena; although the shapes and figure of the leaves afforded much more constant as well as striking characters. The same may be said of his lupinus albus, and luteus; refeda alba, glaucia, and lutea; angelica atro-purpurea; dictamnus albus; lamium album; feligo coccinea; fida alba; passiflora rubra, lutea, incarnata, and cœrulea; and of many others, in which the specific name is derived from a character or quality that is so liable to vary in the same species.
We shall conclude this article with observing, that of all sensible qualities, colour is the least useful in indicating the virtues and powers of vegetables. The following general positions on this subject are laid down by Linnæus, and seem sufficiently confirmed by ex-
periment. A yellow colour generally indicates a bitter taste; as in gentian, aloë, celaudine, turmeric, and other yellow flowers. Red indicates an acid or sour taste; as in cranberries, barberries, currants, rasp-berries, mulberries, cherries; the fruit of the rose, sea-buckthorn, and service-tree. Herbs that turn red towards autumn, have likewise a sour taste; as forrel, wood-forrel, and bloody-dock. Green indicates a crude alkaline taste, as in leaves and unripe fruits. A pale colour denotes an insipid taste, as in endive, asparagus, and lettuce. White promises a sweet, luscious taste; as in white currants, and plums, sweet apples, &c. Lastly, black indicates a harsh, nauseous, disagreeable taste; as in the berries of deadly nightshade, myrtle-leaved sumach, herb-christopher and others; many of which are not only unpleasant to the taste, but pernicious, and deadly in their effects.
To be ascertained of the acid or alkaline property of any plant, express some of the juice, and rub it upon a piece of blue paper; which, if the plant in question is of an acid nature, will turn red; if of an alkaline, green. For the methods of extracting colours from the different parts of plants, see the article COLOUR-Making.
COLOUR of the Human Species, Difference of. Few questions in philosophy have engaged the attention of naturalists more than the diversities among the human species, among which that of colour is the most remarkable. The great differences in this respect have given occasion to several authors to assert, that the whole human race have not sprung from one original; but that as many different species of men were at first created, as there are now different colours to be found among them. Under the article AMERICA, no 42—53. we have shewn that all the arguments which can be brought for specific differences among mankind, whether drawn from a difference of colour, stature, or disposition, must necessarily be inconclusive. It remains, however, a matter of no small difficulty to account for the remarkable variations of colour that are to be found among different nations. On this subject Dr Hunter hath published a thesis, in which he considers the matter more accurately than hath commonly been done, and determines absolutely against any specific difference among mankind. He introduces his subject by observing, that when the question has been agitated, whether all the human race constitute only one species or not, much confusion has arisen from the sense in which the term species has been adopted. He therefore thinks it necessary to set out with a definition of the term. He includes under the same species all those animals which produce issue capable of propagating others resembling the original stock from whence they sprung. This definition he illustrates by having recourse to the human species as an example. And in this sense of the term he concludes, that all of them are to be considered as belonging to the same species. And as, in the case of plants, one species comprehends several varieties depending upon climate, soil, culture, and similar accidents; so he considers the diversities of the human race to be merely varieties of the same species, produced by natural causes. Of the different colours observable among mankind, he gives the following view: