Horticulturists will be anxious to learn what is going on in this department of our coming Centennial. We suppose there will be special exhibitions of various classes of fruits and flowers during the several months that the exposition will continue, but, with the exception of fruits in September, in a measure backed by the American Pomological Society, and which goes into the agricultural department, nothing definite is decided on, at this moment of writing. All effort so far has naturally been centered in the completion of the permanent arrangements. The great conservatory designed by Mr. Swartzman is finished, and is the largest ever built in the United States. It is a very imposing structure, and well calculated to attract the popular eve during an exhibition of this kind. In case there should be any large collections of hot or greenhouse plants on exhibition, as illustrations of superior skill in plant growing, it is remarkably well adapted to the purpose. We have not, however, beard that any of these are offered - this particular department of gardening not having made as yet much headway in our country.

The building is to be permanent - as long as a large structure with so much of wood will remain permanent - and will be an excellent place for the winter storage of large palms, oranges, aloes, tree ferns, and other articles suited to the summer decoration of the Park grounds. The two curvilinear wings are 'vvell adapted to plant growth, and will be a permanent attraction for rare plants. Already many valuable plants are stored in them, the contributions chiefly of Mr. W. E. Smith, of the United States Botanical Garden, and of the Hon. Frederick Watts, of the Department of Agriculture, through Mr. W. Saunders, the Chief Superintendent of that division.

The huge building is heated by eight large hot water boilers, and four miles of iron pipes.

Exhibitors in the out-door departments promise to be numerous. Trees, flowers, fruits, annuals, bedding plants, bulbs, etc, are to be planted out in beds arranged on a plan around the conservatory, each exhibitor selecting a bed from the plan for his own particular articles. These beds are all now completed, and are ready for planting by the exhibitors as soon' as the spring opens. The whole labor of arranging these things has fallen on Mr. C. H. Miller, the Chief of the Horticultural Bureau; and horticulturists may congratulate themselves that the commission was able to command the services of one whose practical knowledge was equal to the task of harmonizing such details with the more popular features which must of course actuate the leading commissioners of such an exhibition.

It is difficult to find out exactly what is being done in the various States in regard to the agriculture and horticulture of the Centennial. From most of our exchanges we learn that everywhere "something" is being done, but we cannot tell exactly what. Of Indiana the Indiana Farmer tells us:

"Thanks to the efforts of Prof. E. T. Cox, our 6tate Geologist, and a few other enterprising and public-spirited citizens, our mineral resources, agricultural productions and educational facilities will have a fair representation. It is a matter of regret that our last Legislature did not make a more liberal appropriation for this purpose, but it is gratifying to know that all will be done that the moderate allowance made, and the too limited subscription fund can accomplish toward giving us a good showing in the eyes of the world."

Instead of reporting what people talk about doing we have thought best to wait till we see what is done, and about this we shall probably be able to tell a little next month.

The exhibition was looked on rather coldly in England for awhile, and, perhaps, considering the superiority of English gardening over ours, it was but natural that it should appeal but little to the sympathies of English horticulturists. The following from The Gardener's Magazine, however, shows that it may not prove wholly unattractive to our English friends:

The International Exhibition of 1876, which will be held in the city of Philadelphia, will in all probability constitute as distinct an epoch in the history of international exhibitions as did the first of the series, held in the lovely palace of glass in Hyde Park, London, in the year 1851. Since then the experiment has been repeated in many of the great cities of Europe, London included, and, though it cannot be said that failure was felt anywhere or any when, until a permanent exhibition was organized at South Kensington, yet there has always been wanting the freshness, the surprise, and the completeness of the first venture, while the partial successes achieved have been more or less prejudiced by a pervading sense of weariness. If any such thing as a great international exhibition is wanted now, the Western continent is certainly the proper place for it. For the present, and for some time to come, the old world has had enough of these things, and it is well that our cousins on the other side of the Atlantic have taken the subject out of our hands, and intend to rehabilitate it in their own thorough and original way of managing such affairs.

The description of the scheme, which will be found in another part of this sheet, will show that the scale is vast and comprehensive, and comprises features now for the first time attempted. All the industrial arts will be fully represented, while agriculture and horticulture will obtain a prominence they have never enjoyed before in similar undertakings, a course of procedure consistent with the requirements of the age as well as with the characteristics of American enterprise and taste.

One of the necessary consequences of the location of the exhibition will be that the old world will visit the new world in considerable force in 1876. Hitherto the traffic across the Atlantic has been chiefly determined by business considerations, for although Americans visit Europe in considerable numbers, very few Europeans visit America, except in obedience to calls of duty or the temptations of commercial advantage. In matters intellectual the people of the States have always had to subsist for the most part on the products of the old world, and the influence on them of European thought has of necessity developed an interest in European scenery and memorials and manners. The playful sarcasm, that "rich Americans when they die go to Paris," represents fairly enough the joyous curiosity with which our Western cousin starts on his tour of Europe, which may be said to begin at Stratford-on-Avon, to culminate at the mosque of St. Sophia, and to end somewhere in the neighborhood of the Tuileries. Between us in respect of such matters the reciprocity, thus far, has been quite partial; for few Englishmen, and in proportion, fewer Continentals, have visited the States unless they were impelled by motives of interest or that conviction of duty which makes the sea as dry land, and converts danger and strangeness into delights which fill the soul with agreeable expectancy.

But a change is coming, and, indeed, has come. The active spirits of the old world are on the move. Philadelphia is the universal goal of the reflective, inquiring, and adventurous ones of Europe, and in an especial manner of all possible English visitors to any possible exhibition. It is early as yet, perhaps, to make the trip, but many whose ruling motive is curiosity are already on their way, and the completion of the exhibition buildings will be witnessed by many nationalities.

The spring of 1876 will see a vast exodus westward, and it is certain that thousands of brave Britons will obtain a glimpse of the United States in a very agreeable way, who would never have sought such a pleasure except through the persuasions of an international exhibition. All will be done that can be done on both sides of the Atlantic to facilitate the movement; but the sea that divides will take its toll of our time, however otherwise it may be disposed to help us. The great Napoleon abolished the Alps by marching over them, and the only way to abolish the Atlantic is to take the fastest ship, and consider the feat of crossing it a nine days' wonder. Some time early in the summer of next year, some great excursion parties will be organized for doing the thing cheap and sociably, and even now various kinds of accommodation are being prepared for the very many who will make the exhibition an excuse for a good look round at the wealthiest cities and most renowned scenes of the western continent; so that many who begin at Philadelphia will have Lake Superior, and Niagara, and Quebec in the programme, and will be wiser when they return than when they went out; or, if not really wiser, certainly richer in observations, and reflections, and comparisons that the "memory will not willingly let die."