I have observed an obstruction in the circulation of the Horticulturist this way, since the reception of the April number. I presume, without looking over my receipts, that the cause is non-payment, which is a good one. I wish every editor in the land would pursue the same course. The Horticulturist is one of the periodicals that I want as long as I am able to take or read a paper, provided it continue as interesting and useful as it now is. I have been a subscriber from its commencement under the auspices of Mr. Downing, and have all the volumes bound.

The climate in this part of Iowa proves too severe for most kinds of fruits, except the hardiest varieties of apples. The two past winters killed all the peaches and most of the cherries to the ground; also, the pears. The exceptions with me, amongst the cherries, were Early May, May Duke, Belle Magnifique, and Heine Hortense; and out of some fifty to sixty varieties of pears, Buffum is the only kind entirely uninjured by the freezing. Both of the winters referred to, the thermometer fell frequently to 20°, and at three or four times from 24° to 28° below zero. Catawba and Isabella Grapes killed to the ground; Brinckle's Orange, Catawissa Raspberries, and Lawton Blackberry, quite hardy. Several others, including Gnevit's Giant, large French Monthly, Ac, killed. All the varieties of currants and gooseberries of course perfectly hardy.

I have taken some pains (as apples must be the principal reliance for those who intend to make their homes in Iowa) to examine and ascertain which are the most hardy and reliable in this vicinity. I have had the aid of Mr. Drury Overton, who is my neighbor, and a nurseryman of seven or eight years' experience here. We have set down as perfectly hardy: Red June, Fall Wine, Jannetting, Smith's Cider, Yellow Bellflower, American Summer Pearmain, Early Sheep's Nose (a very fine apple every way), Newark Pippin, Shaker Yellow (a first-rate apple, ripe in August), Wine Sap, Red Sweet Pippin, Roman Stem, Holland Pippin, Jonathan, Summer Queen, Michael Henry Pippin (no better apple here), Red Sweet Romanite, Green Everlasting, American Pippin, Summer Rose, Red Astra-cean, Belle du Havre.

Clinton Grape proves perfectly hardy with Mr. Overton, and is a prodigious bearer. I ought to say that the two past winters have been an exception. This I know to be so both from the testimony of the first settlers here, and my own observation. I removed to Knoxville in the spring of 1855. There were then in my garden four peach-trees, which, from size and appearance, I should say were from five to six years old, and which bore a fine crop that year. The winter of 1855 and 1856, they were killed root and branch.

Amongst the evergreen sand shrubbery which I have planted out: Scotch Fir (Sylvestris), perfectly hardy; White Spruce (Abies alba), Balm of Gilead (Bal-samea), Blue Spruce (Ccerulea), Norway (Excelsa), and European Silver (Pec-tinata), all hardy, and grow well in our soil; Pines, Austrian (Austriaca), Corsi-can, Russian (Rigensis), and Weymouth, all perfectly sound; Arbor-vitae (American), hardy; Chinese, considerably injured; Ginko (Salisburia), hardy; African Tamarix, killed nearly to the ground. Several varieties of the Box, all injured badly. Yew, common and upright (Hibernica), much injured; Mahonia aquifolia, suffered considerably; Weigelia rosea, perfectly sound. Amongst some twenty-five varieties of Bourbon and Hybrid-Perpetual Roses, all were cut down nearly to the ground, but this injury only seems to increase their propensity for blooming, for I have never seen freer blooming or finer specimens. Amongst the finest, I may name - 1, Mrs. Elliott; 2, Reveil; 3, Bon Paxton; 4, Josephine Robert; 5, George d'Amboise; 6, Sydonie; 7, Duchesse of Sutherland; 8, Felicite of Rigeaux; 9, L'Enfant du Mont Carmel; 10, Madame Trudeaux; and 11, Madame Laffay. The latter has branches now six feet high, made this season. No. 9 is one of the finest roses I have ever seen.

I procured it of Mr. Le Roy, of Angers.

Baltimore Belle and Queen of Prairies, killed down considerably, but still bloom finely; Yellow Harrison, of course perfectly hardy; Syringa, Philadelphus, and Grandiflora, rather tender; Bignonia grandiflora and Radicans, both killed top and root; Wistaria (Chinese) and Periploca, killed to the ground; Persian Lilac, hardy. A few kinds of Spirea are hardy. Japan Quince (Pyrus Japonica), perfectly hardy; Horse-Chestnut will not grow with me in our soil; Mountain Ash, European, American, and Oak-leaved, all perfectly hardy; Weeping and Ring-leaved Willows, killed down.

The foregoing list may be useful to persons emigrating to this State. While we have to deplore the want of encouragement to cultivate the fruits generally, we may well felicitate ourselves on having one of the best agricultural States in the Union. Our crops, this year, are unexcelled. Of all the grains and vegetables, we have a superabundance; and yet, if the unfavorable accounts we have are true in regard to Missouri and Kansas, we shall have a market and paying price for all.

Our farmers and gardeners need none of your bone-dust, guano, or compost heaps, to stimulate the growth of their productions. Nature has bountifully provided us with all the fertilizing ingredients we shall need for half a century, if our lands are properly farmed. With the culture which your Pennsylvania farmers give their lands, our prairies would yield an average of one hundred bushels of corn per acre, and other crops in a like proportion.

I shall have a word or two to say, soon, about my curculio remedy, in regard to which there have been so many hints, suggestions, and inquiries. I have some reports and testimony in relation to experiments made, some with slight modifications, upon my invention, which will, perhaps, place the question in a new light. [Let us have it by all means. - Ed].