IN last month's 'Gardener' Mr Simpson takes exception to an incidental remark of ours, in the August number, on setting Muscat Grapes. He characterises our remark as "exceptional and damaging testimony" against his advocacy of setting Muscats at a temperature of 50°. We want, in the first place, to assure Mr Simpson that we have not the most faint desire to rob him of any credit that may belong to him for the advocacy of this or any other practice. If our practice and experience, and the results thereof, have been different from Mr Simpson's, we cannot very well help that; and our practice in several other matters connected with Grape-growing is not in accordance with Mr Simpson's teachings.

The setting of Muscats is certainly a question of experience, but it is something more, - it is a physiological question as well. And if Mr Simpson expects us to believe that his successful setting of Muscats is the direct result of a night-temperature of 50°, we must believe it on the faith of his, and in spite of our own, experience and observation.

Whether intentionally or not, Mr Simpson does not say to what degree he runs up the heat of his Muscat-house for the greater portion of the twenty-four hours with fire and sun heat. We suspect that the setting of his Muscats, as in the case of other growers, is dependent on having their pollen developed by the higher temperature and drier air of the day, and not by the damp air and temperature of 50° at night, for it is contrary to facts and physiology to think that it can be otherwise. We here appeal to the rank and file of those who have been most successful in producing" really good Muscat Grapes, if it is not when the temperature is 70° to 75°, and not very damp, that Muscat pollen appears in most abundance, and that the berries set best. Perhaps, when we know all, it will be found that Mr Simpson thus runs up the heat of his vinery for the better half of the day; and if we are correct in our supposition, then the relationship of 50° to the setting of his Muscats will appear in its true light.

It has been our experience in a long practice under divers circumstances, that Muscats have, without an exception that we can remember, set best when they have been subject to a high temperature for the greater part of the twenty-four hours. Not only so, but they have always set best at the hottest end of the vinery and nearest the pipes, as in the case of J. W. B., related in the ' Gardener' of last month. It would be interesting to know how Mr Simpson manages always to get his temperature down to 50° after a warm day and the application of fire-heat in May. We cannot do it, practising much farther north. We presume, from the condition of his Grapes about the middle of September, that his Vines are not more advanced than in bloom in May.

Not to go any further back in our experience, we had a house of Muscats in bloom last May, when the weather was exceptionally cold and sunless, - circumstances under which we think it best to force more gently. Those at the warm end of the house set perfectly, while three rods at the exposed gable and cold end set so very imperfectly that there were not sufficient impregnated berries to make up the bunches. Will Mr Simpson explain the reason of this? The Vines were the same variety, and all their circumstances exactly the same, except that the one was in a very much colder atmosphere than the other when in bloom. What is the opinion of other Muscat-growers ?

We do not controvert the fact, that it is best for plants to treat them to a lower temperature at night than by day. Nature leads the way in this very forcibly; and it has been practised and written about as long back as we can remember - forty years at least. But nature does not teach us that it is the damp cold air of night that develops the pollen, and is directly to be credited with the setting process. We learned this quite forty years since from Dr Lindley : "It will be found that no pollen is scattered in cold weather, but in a sunny, dry, warm morning the atmosphere surrounding plants is, in the impregnating season, filled with grains of pollen discharged by the anthers. In wet weather the anthers are not sufficiently dried to shrivel and discharge their contents," etc. Because of this there is nothing the Vine-growers of France dread more than a wet, cold, sunless time when their Vines are in bloom; for the bunches, instead of flowering properly and developing pollen, do what the Vine-growers call "run." De-caisne refers to this fact in his work on botany, when treating of physiology.

It has long been well recognised that when the bunches of Grapes have a tendency to be "wiry" and "run," that the best way of checking this tendency is to keep them rather warmer and drier instead of colder and damper. We have advocated comparatively low night-temperature in hothouses a good many years ago, but have never yet seen cause to alter our opinion or practice in setting Muscats, and are as convinced that a rather high temperature for the greater part of the twenty-four hours when the Vines are in bloom secures the best set, as we are of anything connected with the practice of horticulture.

All theory and practice are best tested by results; and unless better examples of Muscats are exhibited as grown on the very low temperature system than are produced under higher temperatures, the advocates of a warmer temperature can well afford at least to wait.

More than thirty years ago we have seen splendid Muscat Grapes ripened in August, and cut from the Vines plump and fresh on the 16th of March. And these Vines, in spite of some very rough treatment, are fine Vines at this date. We have for years in succession started Muscats in February, ripened them to an unusually high colour before the end of July, and cut them without a wrinkle from the Vines in the end of February.

It is our opinion and conviction, founded on long practice and observation, that to make October, or even the end of September, the finishing time of Grapes, and more especially Muscats, is one of the greatest mistakes possible. Grapes, and especially Muscats, ripened so late, cannot possibly be of such fine quality nor keep so well as when ripened earlier under the influence of more sun. We once had a Lady Downes Vine at the warm end of a Black Hamburg house, where the fruit of the latter was ripened for using in July. The Lady Downes in question ripened thoroughly in August, and the Grapes always kept longer without signs of shrivelling and decay, and were better flavoured than others ripened a month or six weeks later. And we appeal to successful Grape-growers if Muscats do not always keep the longest in good condition, and are in every point better, that ripen and colour perfectly before the middle of September. Few Grapes keep better than perfectly ripened Muscats. Whoever attempts to ripen Muscats that are green and unripe at the middle of September, must be in a very favoured locality indeed if they accomplish their task without a considerable expenditure of coal.

Is this not so, ye Johnstons, M'Kelvies, Hunters, and Hammonds, and many others besides 1.