it is only as plants advance in age that the secretions necessary for the perfect production of either the one or the other are elaborated. Of this fact, the first produce of the Black Eagle Cherry tree afforded a striking example. A part of it was sent, with other cherries, to the Horticultural Society; and it was then, in the Fruit Committee, pronounced good for nothing. It was so bad, that Mr. Knight, who raised it, would most certainly have taken off the head of the tree and employed its stem as a stock, but that it had been called the property of one of his children, who sowed the seed which produced it, and who felt very anxious for its preservation. It has now become one of the richest and finest fruits of its species which we possess.

It may be expected that some mention should here be made of double flowers, and of the manner in which they are to be obtained. But I confess myself unable to discover, either in the writings of physiologists, or in the experience of gardeners, or in the nature of plants themselves, any sufficient clue to an explanation of the causes to which their origin may be ascribed. There are, however, several facts apparently connected with the subject, which deserve mention.

A double flower, properly so called*, is one in

* What is called a Double Dahlia is misnamed; and so are all so-called double Composite flowers. The appearance of doubling is caused in these plants by a mere alteration of the florets of their disk into the form of florets of the ray; a very different thing from double flowers. (83.)

which the natural production of stamens or pistils is exchanged for petals, or in which the number of the latter is augmented without any disturbance of the former; in other words, it is a case of the loss, on the part of a plant, of the power necessary to develope its leaves in the state of sexual organs. (83, 84.) But what causes that loss of power we do not know. It can hardly be a want of sufficient food in the soil; for double flowers (the Narcissus, for instance) become single in very poor soil. On the other hand, it can scarcely be excessive vigour; for no one has ever yet obtained a double flower by promoting the health or energy of a species. When plants are excessively stimulated by unusually warm damp weather at the period of flowering, their flowers in such cases sometimes become monstrous: but the effect of this is to lengthen their axis of growth, and to form true leaves instead of floral organs (84. fig. 14.), just the reverse of what occurs in a truly double flower; the varieties of Rosa gallica often exhibit this kind of change. In damp cloudy summers, some flowers assume the appearance of being double, by the change of their sexual organs into small green leaves, as occurred very generally to Potentilla nepalensis in the summer of 1839, a representation of which is given at page 62.; but there was, at the same time, scarcely a trace of any tendency, on the part

of those leaves, to assume the colour or texture of petals.

There is, evidently, a greater tendency in some flowers to become double than in others, and especially in those having great numbers of stamens or pistils. All our favourite double flowers, Hepaticas, Pæonies, Camellias, Anemones, Roses, Cherries, Plums, Ranunculuses, belong to this class; and, in proportion as the natural number of stamens diminishes, so do both the disposition to become double, and the beauty of the flowers when altered. The Pink and Carnation with ten stamens are the handsomest race next to those just mentioned; while the Hyacinth, the Tulip, the Stock, and the Wallflower with six stamens, and the Auricula and Polyanthus with five, form altogether an inferior race, if symmetry of form, and regularity of arrangement in the parts of the flower, are regarded as beauties of the highest order. If the mere circumstance of a plant having but a small number of stamens be a bar to its beauty when made double, how much greater an obstacle to it must be the natural production of unsymmetrical flowers. This occurs in the Snapdragon, which, with a five-lobed corolla, has but four stamens; and the consequence is, that, when it becomes double, the flower is a confused crowd of crumpled petals issuing from the original corolla.

I have heard of attempts to produce double

flowers by artificial processes, but I never heard of the smallest success attending such cases, unless the tendency to their production had already manifested itself naturally; as in the Stock, which will frequently become single from having been double, in which case its original double character may be recovered. A mode of effecting this has been described by Mr. James Munro. (Gard. Mag., xiv. 121.) Having a number of Single Scarlet Tenweek Stocks, he deprived them of all their flowers as soon as he found that five or six seed-vessels were formed upon each spike, by which means he compelled all the nutritive matter that would have been expended upon the whole flower-spike and its numerous seed-vessels to be concentrated in the small number which he left; and the result, he says, was, that from the seed thus saved he had more than 400 Double Stocks in one small bed.

There can, I think, be no doubt that, if any original change to a double flower can possibly be effected by art, it will be more likely to occur with respect to those species which have an indefinite number of stamens, where the tendency to this

monstrosity already exists. It is not many years since the Chryseis (Eschscholtzia) californica, a polyandrous plant, was introduced to our gardens; and I, at one time, made some attempts to render it double, conceiving it a good subject for experiment on that account, but I had no success; it

has, however, accidentally become semi-double in Mrs. Marryat's garden, at Wimbledon; and I entertain no doubt that seed skilfully saved from that plant would present its flowers in a still more double condition.

CHAP. XIX.

OF RESTING.

A GARDENER is said to rest a plant when he exposes it to a condition in which it cannot grow, and which is analogous to its winter state. For many parts of gardening, especially what relates to forcing and the management of exotic plants, this is a subject of the first importance.

If we look over the different climates of the world, we shall find that in each there are a season of growth, and a season in which vegetation is more or less suspended; and that these periodically alternate, with the same regularity as our summer and winter. I do not know that there is in nature any exception to this rule: for even in the Tierra templada of Mexico, where it is said that, at the height of 4000 to 5000 feet, there constantly reigns the genial climate of spring, which

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