FORCING THE MUSHROOM. 523 



belonged to P. C. Labouchere, Esq. (See G. M. vi., p. 691 ; viii., p. 174, 

 and iii. p. 388.) 



1110. Perennial pot and sweet herbs, such as mint, sage, tarragon, savory, 

 thyme, tansy, scurvy-grass, and such like plants, may be taken up from 

 the open ground, potted, and transferred to the forcing-house, where they 

 will soon produce abundance of foliage ; care being taken to let the heat 

 with which forcing is commenced be low, in proportion to the coldness of 

 the country of which the plant is a native, and that of the season at which 

 it naturally expands its leaves. Thus, in forcing scurvy-grass, which is a 

 native of Denmark, a much lower temperature ought to be commenced with 

 than in forcing sage, which is a native of Greece ; and again, a plant which 

 naturally springs up in April will bear commencing with a higher tempera- 

 ture than one which makes considerable progress in the previous colder 

 months. 



SECT. XV. Forcing the Mushroom. 



SUBSECT. I. Data on which the Culture and Forcing of the Mushroom 

 is founded. 



1111. The mushroom (Agaricus campestris L.) is indigenous to Britain, 

 appearing " in the fields chiefly after Midsummer, in the months of July, 

 August, and most abundantly in September. On a ten years' average, the 

 temperature of these months respectively in the neighbourhood of London 

 has been found to be 64, 02, and 57 ; and in the same periods the tempe- 

 rature of the earth one foot below the surface is a few degrees higher ; but 

 at the depth of two or three inches, where the vegetating spawn is situated, 

 the temperature in hot sunny weather is frequently as high as 80. Whilst 

 such hot weather continues, mushrooms are rarely met with ; but when the 

 atmosphere changes to a humid state, and when the earth becomes suffi- 

 ciently moistened and lowered in temperature, in consequence of rain and 

 absence of sun-heat, to be between 60 and 65, mushrooms become plenti- 

 ful. Hence it may be concluded that spawn will not be injured by a heat 

 of 80 during what may be termed its underground state of progression. 

 This is corroborated by the fact that spawn introduced into melon-frames 

 when the beds are moulded, increases whilst the melons are grown in a heat 

 of about 80 ; and when the melon crop is over, the frame cleared, and the 

 heat of the bed naturally abated, a gentle watering, with shade, is all that 

 is necessary to bring up an excellent crop of mushrooms from the spawn so 

 deposited. It is evident, from what has been stated, that the spawn requires 

 a high temperature for its diffusion ; but, when this has taken place, a 

 declining temperature is requisite, till gradually the bottom-heat is lowered 

 to 60 or 65, and the temperature of the air limited between 55 and 65, 

 when the production first appears above the soil. 



" With regard to moisture, it may be observed that a dry atmosphere is 

 injurious, not only to artificial crops, but also to those in the fields ; for the 

 latter, warm foggy mornings are most favourable, and these should be imi- 

 tated as closely in cultivation as circumstances will permit. A gentle steam 

 is more easily maintained in mushroom-houses than in structures adapted for 

 other subjects of cultivation where light is an object of importance ; but 

 mushrooms do not require its agency, and consequently a glass roof is unne- 

 cessary : on the contrary, the roof and walls where they are intended to be 

 grown should be composed of such substances as will cause the least possible 



