The emphatic negative given by Mr. Allen, in the May number of the Horticulturist, to the question, "Can Pears be profitably grown for the market/' has brought out by way of reply, equally ardent articles in the affirmative from those who have been more successful. I trust Mr. Allen's impulsive and enthusiastic way of presenting any cause which he adopts, will not subject him to the fate of the French editor, who, for his remarks upon the manners of the military, was compelled to accept challenges to fight one hundred lieutenants, seriatim, provided he survived the onslaught of the first ninety-nine.

Local reasons may be assigned for Mr. Allen's failure, but the same local reasons prevail pretty extensively elsewhere, and Mr. Allen with his misfortunes will be regarded by a considerable class of pomologists as a representative man. That upon sundry belts and strips of territory in the State of New York, where the heat and cold of the respective seasons are modified by the proximity of large bodies of water, that about Boston and Rochester, and within circumscribed limits elsewhere, the Pear under favorable features in the climate, and friendly aliments in the soil, can be grown with great success is undoubtedly true, and that the delicious character of the fruit there grown justifies all the enthusiasm exhibited by the producers is equally true. But is also certain that a large, very large proportion of all the pear trees set out north of 31° 30' perish in the course of eight or ten years after planting.

Nurserymen and planters may criminate and recriminate each other, but the great difficulty, I apprehend, will be found to be in the severity of our northern winters, and the violent changes of temperature at times incident to our climate. On the highlands, where the hills reach an altitude of four or five hundred feet, and where the temperature is lower and more uniform than it is in the valleys, the durability of the Pear*tree is greater and the chances of fruiting it better; but on the low grounds throughout the western country, within the last five years, not only have the peach, pear, and cherry trees been destroyed, but thousands of apple trees of thirty and forty years' growth have been killed to the ground. Within eighteen years, I have grown up and lost two sets of pear trees with varied success as to fruiting them. The third set in my garden were covered last fall before any cold weather set in, and the straw left on them until about the first of May; yet on heading them back, the wood was found to be considerably discolored.

And though they are making, with the abundant rains we have had, a vigorous growth, and may not this year exhibit any bad effects from it, yet I doubt whether a tree can be affected to discoloration for several seasons without ultimately exhibiting disease and premature decay. There is much that re compensatory in the interest created by fruit culture even with indifferent success. A series of mild winters occasionally allows to the cultivator a full reward for his labors, and while the chances in the pomological lottery remain, even as good as they now are, there is not much danger of a failure in either the supply or demand, even should the blanks as well as the prizes be presented for the consideration of the public.

Those who are discouraged with frosts, and the curculio, with blight, and black knot, can enjoy a great variety of the most wholesome fruit in the world for four or five months in the year, by growing grapes under glass. And while on this subject, permit me to say that Mr. Saunders and myself do not differ much in practice in giving free nocturnal ventilation after the fruit has set. In a late article, he points out that permitting a change of from thirty to thirty-five degrees between the temperature of the day and night, is better than the eight or ten degrees recommended in the books.

I have not found that a change even of forty degrees does any apparent harm to the vines, which I suppose is as great as ever occurs at Philadelphia, but here we have occasionally greater extremes; thus on the twelfth of this month, (June,) the thermometer sank to forty degrees; and on the twentieth of June last year it sank to forty-five degrees. Such violent changes, I think, should be counteracted by closing the house, and to this I suppose Mr. S. would assent.

I made a report to the Horticulturist two years ago, upon some vines fruited the second season after planting, and the products of a grapery only twenty by twenty-two feet. The yield has continued to be over four hundred bunches per year, ranging from half a pound to a pound and a quarter in weight. Last season, long-continued rains injured a portion of the crop with mould - a difficulty 1 believe experienced elsewhere as well as here. For two nights in succession this spring, on the 26th and 27th of April, the temperature fell according to a self-registering thermometer in the grapery to within nineteen degrees of zero. The first and strongest buds, then some three inches grown, were destroyed, and the crop will this year be " somewhat lighter than it was last.

I have never used any fire heat, nor have ever before had the fruit injured to any extent by the frost. I would advise any one building a cold.grapery to make arrangements for a stove to guard against the above contingencies.

All my experience demonstrates the very great superiority of a grapery with an east and west over one with a southern exposure. The sun breaking out some cool day when the ventilators are closed, heats up the latter as suddenly as a hot bed, and it requires fully double the attention in this respect that the other does. I noticed last year that some Hamburgh grapes, growing high upon the trellis where they no doubt got rather too much sun and heat, were mere skin and juice, while those growing more in the shade and among the foliage were more palatable, with a sweeter and more substantial pulp. The Diana, unlike what its alleged parent, the Catawba, is said to do, grows thrifty and fruits well under glass.

The controversy about the genuineness of the Rebecca grape vines supplied from Massachusetts, seems to have been put at rest by establishing the purity of the article with a North River responsibility as to the quality.

We are often told about the propriety of purchasing from regular dealers, if we want a good article from the nurseries. I trust the regular dealers will not compromise the good character they enjoy, by sending out any more such insignificant plants, as were some of these Rebecca grapes. It is fair enough to charge a high price for a new vine of superior merit, but to give a buyer a plant of microscopic proportions which requires a bell glass for a fortnight to coax it into vitality, is not what he expects for his money, nor does a cultivator wish to spend four years in growing up a vine which, if properly started, can be produced in half of the time.

I shall be pleased to learn through Mr. Saunders or some of the Philadelphia cultivators, whether the Emily grape proves hardy enough for outdoor culture without protection.