VEGETABLES UNDER GLASS. 187 



get along without at least a hotbed, while in the large market 

 gardens the glass is measured by the acre. 



The hotbed, being of simpler construction than the greenhouse, 

 was used by gardeners earlier than the greenhouse, and even now 

 has many advantages in the spring of the year, especially in 

 growing plants for setting out in the open air; the ease with 

 which the bed can be freely aired, or on fine days exposed 

 entirely to the open air, by removing the glass, is a point not to 

 be attained under the permanent roof of the greenhouse. 



Boston gardeners have for about fifty years grown lettuce for the 

 New York market, and even now it is probable that more than 

 half of the lettuce grown near Boston is consumed in the great 

 metropolis. At first it was grown only in hotbeds, and gardeners 

 seemed to think that it could not be grown of good quality unless 

 within a few inches of the glass; but about twenty-eight years 

 ago some of the gardeners of Newton and Belmont began to 

 experiment in building greenhouses, being forced to this by the 

 scarcity of horse manure, which was used by the Arlington 

 gardeners in great quantities for their hotbeds ; indeed at this time 

 the number of hotbeds on many farms was limited only by the 

 amount of manure that could be bought. The price of manure 

 was then about six to eight dollars per cord in Boston ; at present 

 it is worth from one dollar to nothing at all. Hotbeds, however, 

 have not entirely gone out of use ; indeed there are probably more 

 of them used now than ever before ; but much the larger part of 

 the increase of glass for vegetal^le growing during the last twenty 

 years, has been in the construction of new greenhouses. 



Hotbeds. — The construction of hotbeds, as described in many 

 Ibooks on gardening, is a much more expensive method than is at 

 all necessary, or than is followed by most practical gardeners. 

 There is no need of using nearly so much "heat" as the books 

 usually advise, and a bed sunk in the ground so that the glass 

 shall be only a few inches above the general surface, is far easier 

 to build and to manage, than one heaped up two or three feet high, 

 as is often advised in the books. 



The hotbed is usually built in November. The location selected 

 should be well drained, with a nearly level surface ; if it slopes 

 slightly to the south or south-east it will be better. The work is 

 commenced by building a tight board fence, six and a half feet 

 -high, running nearly east and west. The posts for the fence are 



