In some genera with irregularity of flower often less marked than in previous examples, it is worthy of notice that the two divisions on each side of the odd lobe frequently partake of its characters as regards colour, half of each resembling the odd piece, as may be seen in Viola, Gloxinia, Achimenes, Rhododendron, and other plants.

3. In certain Thalamiflorous Exogens with unequal corolla, arising chiefly from difference in size of the petais, the largest are most highly coloured.-Common horse-chestnut may be mentioned as an example; on each petal there is usually a crimson spot at the lower part; the size of this spot and its intensity are in direct relation to the size of each petal, the two upper being largest, and the two lateral smaller, and the odd piece least of all.

4. Different forms of corolla in the same inflorescence often present differences of colour, but all of the same form agree also in colour.-The family of plants called Compositæ, comprehending Aster, Cineraria, Daisy, &c., &c., presents illustrations of this. When there are two colours, the flowers of the centre, usually of tubular form, have generally one colour of uniform intensity; those of the circumference, having a different form, agree together in colour also. Thus the common daisy has all the tubular flowers of the centre yellow, and all the ligulate (strap-like) flowers of the ray or circumference are white, variegated with purple. A yellow centre with a purple ray is a common association in Composite; for instance, in species of Aster, Rudbeckia, &c. These principles or laws prevail as well in monocotyledons as in dicotyledons. In the former, the calyx and corolla generally resemble each other in structure and shape, and in colour also. This very close resemblance between the two

whorls has given rise to the idea that there is only one series of external parts in monocotyledons. Relative position must, however, not be overlooked, and hence it is concluded that both calyx and corolla are present. In dicotyledons we generally find a greater contrast between calyx and corolla as regards colour. We may say therefore,

5. The law of the contrasts in the colour of the flower is simpler in monocotyledons than in dicotyledons.— The flowers of dicotyledons may be symbolized by the square or pentagon, four and eight, five and ten being the prevalent numbers in the different whorls; whereas since three and six are generally found in the flowers of monocotyledons, the triangle may serve to symbolize such arrangement. Such comparison is not fanciful on our part, but an actual statement of the mode of illustration adopted by botanists. Thus, in a work by one of the highest authorities of the day, a series of triangles is used for the purpose of demonstrating, more clearly than could be done by any other means, the true relations of the flower in the families of the grasses, palms, and orchids.

We may state in conclusion, therefore, that simplicity of figure corresponds with simpler contrast of colour in the monocotyledons, while greater complexity of colour and greater complexity of structure are in direct relation in dicotyledons.-In all these remarkable co-existences there is surely something more than mere casual coincidences. As the laws of the beautiful have not been detected and unfolded, it is not possible to demonstrate scientifically that the relations we have been treating of are in accordance with æsthetic principles. But the eye at once perceives in regard to some of these arrange

1 Lindley's Vegetable Kingdom, pp. 109, 169, 178.

ments, that they tend to enhance the beauty of the plant. Would not reason be offended if uniform flowers had not uniform colouring? Is there not a propriety, when in an irregular flower there is one petal standing by itself, that that petal should have more brilliant colours, that thus the flower may be tempered together, having more abundant honour in the parts which lacked, that there be no schism in the plant? We are persuaded that were we to put a flower without any colour into the hands of a skilful colourist, and ask him to put on the colours, he would do so on the very principles according to which plants are coloured in nature.

Proceeding on the principle that since plants of all epochs of the earth's history have been constructed on the same general plan, so the same associations of colour, and of colour and form, must have prevailed also, we may finally glance at a few conclusions to be derived from this source.

During the earlier geological periods, when Acrogenous Cryptogamia (Ferns, &c.) were abundant, the secondary and tertiary colours, as green, purple, russet, and citrine, probably prevailed.

During the reign of Gymnosperms, when Cycadeæ and Coniferæ were numerous, the secondary and tertiary colours must still have given a sombre aspect to the vegetable world.

From the commencement of the chalk formation there appears to have been a very marked and progressive increase of Angiospermous dicotyledons, which form the largest proportion of existing vegetation. Among them we find the floral organs with greater prominence in size, form, and colour; and such prominence of the "nuptial dress" of the plant, is peculiarly a feature of species belonging to natural families which have attained their

maximum in man's epoch, and are characteristic of it. Brougniart, one of our highest authorities in this department, states that a remarkable character of the floras of the eocene, miocene, and pliocene epochs-which immediately preceded man's epoch-is the absence of the most numerous and most characteristic families of the Gamopetala. Nothing announces the existence of Compositæ, Personatæ, Labiatæ, Solanaceæ, Boraginaceæ, &c.

Doubtless there were lovely flowers in former periods, "born to blush unseen," at least by human beings, but we miss those which are our special favourites, and whose cultivation is one of the characteristics of civilized man.

We cannot avoid thinking that there was design in all this, that the succession of created forms in the vegetable kingdom had a reference to the epoch of man; and that just about the time when there appeared an eye to receive and convey the impressions of beauty, and an intellect to derive satisfaction from the contemplation of such, then it was that the most highly adorned productions of Flora's kingdom were called into existence.

SECT. II.-ADAPTATION OF THE COLOURS OF PLANTS TO THE NATURAL TASTES OF MAN.

Artists lay it down as a maxim that a large portion of a painting should be of a neutral colour. Our natural tastes would not tolerate a scarlet or purple ground to a historical painting. In a skilful piece of art the more prominent figures are made to rise out of colours which attract no notice. It is the same in the beautiful canvas which is spread out before us in earth and sky. The ground colours of nature, if not all neutral, are at least

1 Annales des Sciences Naturelles, 1849

2 In Gamopetalæ there is adhesion of petals; the flowers are tubular.

all soft and retiring. How grateful should we be that the sky is not usually dressed in red-that the clouds are not painted crimson-that the carpet of grass on which we tread is not yellow, and that the trees are not decked with orange leaves! The soil, in most places, is a sort of brown-the mature trunks of trees commonly take some kind of neutral hue-the true colour of the sky is a soft blue, except when covered with gray clouds, and the foliage of vegetation is a refreshing green. It is out from the midst of these that the more regular and elegant forms, and the gayer colours of nature, come forth to arrest the attention, to excite and dazzle us, not only by their own splendour, but by comparison and contrast.

All the gayer colours of the vegetable kingdon seem to be beautiful in themselves. The eye needs no associated object to lead it to detect a loveliness in the red rose, and the blue harebell, and the yellow primrose. But there are associations of colour in art which have a pleasing effect upon the mind. In our Schools of Design pains are taken to shew what colours may be placed in juxtaposition, and what colours may be kept at a distance from each other. In the construction of tapestry, and other kinds of higher needlework, in the manufacture of our finer texture of fabrics, and in the staining of glass for windows, strict attention is now paid to rules on this subject, prescribed by science and sanctioned by experience. We proceed to shew that in nature colours have been associated from the beginning, according to principles which have become known to man only at a comparatively late date in the history of human civilisation and science. In order to explain this, it will be needful to begin with a few elementary statements in regard to light and colour.