wanting to confirm this conjecture; though the latter propably originates from soil or situation, and may be communicated by ingrafting.—The origin of new colours in flowers, and of variegated foliage, is imagined to arise from the want of nourishment of the soil on which they grow, compared to that assigned to them by Nature: or from a defect of moisture and of heat; a supposition countenanced by the dwarfish size of such plants, in general, and especially by the reduced stature of tulips, when their petals acquire various colours.
The immediate cause of the various colours presented by some flowers, such as poppies, has not hitherto been distinctly ascertained; but Dr. Darwin conjectures that, as they are not variable by the obliquity with which they are seen, like those of mother-pearl, card-fish, &c. they do not depend on the thinness of their pellicle, and may, therefore, arise from the greater facility which some parts of vegetables, more than others, possess in parting with their oxygen (which see) when exposed to the sun's light; for all flowers are more or less blanched before they first open.
3. The origin of double flowers is believed to result from the luxuriant growth of the plant, in consequence of excessive nourishment, moisture, and warmth: they arise from the increase of some parts of the flower, and the consequent exclusion of others. As they present a greater blaze of colour in a small space, and continue in bloom for some weeks longer than single flowers, the method of producing them from seeds is a matter of importance. Botanists very properly term such multiplied flowers vegetable monsters, because they possess no stamens or pistils, and therefore can produce no seeds.—Nevertheless, they are frequendy raised immediately from seeds; because flowers cultivated with more manure, moisture, and warmth than is congenial to them, not only grow larger and more vigorously, but likewise shew a tendency to become double, by having one or two supernumerary pestals in each flower, such as the stock July flower, cheiranthus, and anemone. It is stil lmore remarkable, that this duplicative is communicated to those individual blossoms: hence florists tie a thread round such flowers, to mark them, and to collect their seeds separately, from which double or full flowers are said to be uniformly produced, if they be cultivated with additional manure, moisture, and warmth, as has been already observed.—There subsists a curious analogy, concludes Dr. Darwin, between these vegetable monsters and those of the animal world; for a duplicature of limbs frequently attends the latter, as chickens and turkeys with four legs and four wings, and calves with two heads. In mules, also, the most important organs become deficient, so that they cannot propagate their species; exactly analogous to these full flowers which, from the same cause, produce no seed. With respect to botanic systems, it may be observed from these vegetables of exuberant growth, that the stamens and pistils are less liable to change than the corols and nectaries; consequently, that they are more proper parts for arranging plants into classes; and that on this idea Linnæus constructed his unrivalled system. Lastly, the calyx,
