522 FORCING THE MUSHROOM. 



lettuces on their tables every day in the year. The seed is sown on 

 the 1st of September, and when the plants have produced their fourth 

 leaf they are transplanted into a melon-bed which has done bearing ; 

 and as soon as they have taken root, abundance of air is given night 

 and day. In October, when the air grows cold, and the heads of the 

 cabbage-lettuce begin to get close and hard, air is no longer given, 

 and the lights are entirely closed ; but the leaves must be prevented 

 from touching the glass, as, if they do, the least unexpected frost will 

 hurt their edges, and the consequence will be that the plants will rot. 

 In this case the frame will have to be lifted every now and then. 

 When the nightly frosts commence, generally in October, great atten- 

 tion must be paid to covering the beds with a single layer of bast mats, 

 and adding slight linings ; yet too much covering is to be avoided 

 before the plants are grown to perfect heads. Watering is quite out 

 of the question, and even very hurtful ; care, indeed, should be taken 

 to prevent moisture as much as possible. Cover more or less, according 

 to the severity of the weather, and keep the lights uncovered in the 

 day, whenever and as much as the weather will permit. In this way 

 the Dutch gardeners produce cabbage-lettuce during the whole winter 

 till April, when they are succeeded by the plants which have been 

 early forced. Perhaps the most successful of all cultivators of winter 

 lettuce are the French, who grow them in frames and under the cloches 

 elsewhere described in this book. The cloches, when used for forcing, 

 being always placed on a gentle hotbed, while by the use of the cloche 

 alone, without the hotbed, beautiful crops of early lettuce are annually 

 raised round Paris. 



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

 thyme, tansy, scurvy-grass, and similar 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 na.tive 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 temperature than one which makes 

 considerable progress in the previous colder months. 



Forcing the Mushroom. 



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 neigh- 

 bourhood of London has been found to be 64, 62, and 57 ; and in 

 the same periods the temperature 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 



