Floral and Horticultural Exhibitions. - We were present at that of the Manchester Floral and Horticultural Society, held on the 27th of June, and we must say we have never seen any thing of the kind equally splendid in the meeting-room of the Horticultural Society in Regent Street. We have seen much better fruits in the latter place; but so many large well-grown specimens of hot-house, green-house, and hardy plants in pots and tubs we never saw assembled together before. We were assured by gentlemen connected with the Society, that since its establishment the horticulture and floriculture of the neighbourhood of Manchester have greatly improved. From 500l. to 600l. a year are given away in prizes; and so eager are even the wealthy to obtain these, that the very newest and most expensive plants are obtained from London with a view of flowering and exhibiting them in competition. The Botanical Register and Botanical Magazine are eagerly looked over every month for novelties, and the order instantly sent, to insure a supply in case there should be only a few plants to dispose of. We believe that this kind of competition for prizes in the country, and on the Continent, is a main source of support to some of the growers of the more rare plants about London.