G44 



THE PRACTICAL GARDENER. 



times with saw-dust; in such cases, the enclosed lining was 

 left uncovered, as the steam proceeding from it could not in- 

 jure the crop ; by this method we gained more heat, but the 

 state of the crop was not so readily ascertained as by the other 

 method. Rhubarb, when required to be blanched, may be 

 managed exactly in the same way ; but where there is the 

 convenience of forcing-houses at work at this season, it is not 

 worth the expense and trouble. The covers should not be so 

 high as to form too large a space under them to be heated ; if 

 eighteen inches in their highest part, it will be amply sufiicient. 



FORCING MUSHROOMS. 



Where mushrooms ai*e required all the year, they cannot be 

 liad without some degree of artificial heat, and therefore may 

 come under the head of forced vegetables. The most suc- 

 cessful and convenient method of producing this vegetable 

 during winter is decidedly that introduced by Mr. Isaac Oldacre 

 late gardener to Lady Banks. It is the common method ot 

 cultivating mushrooms in Germany, and by him introduced 

 into Russia, during the time he was one of the gardeners to 

 the late Empci'or. It was subsequently adopted by him at 

 Spring Grove, and now, with slight variations, almost univer- 

 sally practised throughout the British gardens. The house in 

 which the mushrooms are grown may either be a detached 

 building, or may be erected behind a pine-stove, or other hot- 

 house, and of dimensions according to the quantity of mush- 

 rooms required. 



The mushroom-house of Oldacre, of which the accompany- 

 ing figures are representations, is described by him in a com- 

 munication to the London Hort. Soc. as follows : " The out- 

 side walls (g h) should be eight and a half feet high for four 

 heights of beds, and six feet and a half for three heights, and 

 ten feet wide withinside the walls. This is the most conve- 

 nient width, as it admits of a set of shelves three feet and a 

 half wide on each side, and affords a space through the middle 

 of the house three feet wide for d double flue, and to walk 

 upon it. The wall should be nine inches thick, and the length 

 of the house as it may be judged necessary. When the out- 



