This section is from "The Horticulturist, And Journal Of Rural Art And Rural Taste", by P. Barry, A. J. Downing, J. Jay Smith, Peter B. Mead, F. W. Woodward, Henry T. Williams. Also available from Amazon: Horticulturist and Journal of Rural Art and Rural Taste.
Copper pipes had their advantages. They become heated rapidly, but part with the heat as rapidly. A house can be heated in a comparatively short time by copper pipes. Tanks had been in use, but the difficulty of making them perfectly tight was a defect, and they have been discarded. The escape of steam was also an objection, as it was injurious to plants in many cases. Tanks might be used in connection with pipes.
With reference to Br. Warder's remarks referred to by the last speaker, I may say that I do not, from a perusal of them, as reported in the "Cincinnaiw," consider them at all final, but leaving the subject as much confused as before. There are several passages in it to me quite objectionable, but to which I will not at present allude. The statement of the old ground that we must know the constituents of the plant, and the constituents of soil, has nothing final in it. I should like to know from Prof. Stephens, what is his opinion of this part of the question, since chemists themselves admit that, although they may analyze a handful of soil, the result is no reliable, practical guide to the cultivator.
Damp had been adduced as the cause of mildew, but I can not agree with this conclusion. It has been asked, how shall we prevent mildew in graperies? I say, by admitting little air, and no air below. If mildew be caused by damp, how do we account for the absence of mildew on the gooseberry in the moist climate of Scotland. I may also mention that, while in New Haven, Conn., we had a very damp season in 1850, and there that year I had fine gooseberries, free from mildew. The lilac here is not affected in wet seasons as it is in dry; and the hawthorn - what destroys the hawthorn in this climate, but our dry, hot summers? There is nothing scientific about this matter; if we can prevent this dry, arid air, we can remedy all this. All the remedies applied have acted by producing this result: for instance, salt hay is used to mulch the gooseberry, and, by preserving moisture, prevents the mildew. The mildew on bread has been spoken of as an example that damp produces these fungi; but bread-mildew is not vine-mildew; the idea of mildew seems to be associated with the idea of dampness, but these various forms are various species of fungi. We are told by Lindley, in his Theory of Horticulture, that dry air, acting on tender vegetable tissue, will produce disease.
We may set aside the scientific part of the question entirely, and arrive at a proper conclusion. If plants are kept in a house, in a nice, moist, growing atmosphere, they will never mildew. As to European forms of mildew, they are not identical with ours. Grapes are not mildewed in England or Scotland, and the plants that are generally subject to mildew are natives of a country with a more humid atmosphere than ours.
How is it then, that they are more prevalent in dry weather?
Another fact may be quoted, in relation to the Virgalieu, or butter-pear. This is rendered worthless in low grounds by cracking and sporting. In city yards it is generally exempt. This is owing, in my opinion, to the protection of the trees by the walls and houses, so that dry currents are prevented.