GREENHOUSES WITHOUT ARTIFICIAL HEATING. 185 



in the pit. If the soil is moist it should be drained, 

 and the bottom covered with an inch or two of cement. 

 The sides of the pit may be either walled up by a four 

 or eight-inch course of brick work, or planked up, as 

 may be preferred; but in either case the back wall should 

 be raised about eighteen inches and the front about six 

 inches above the surface, in order to give the necessary 

 slope to receive the sun's rays 

 and to shed the water. A 

 section of such a pit is shown 

 in figure 64. If a pit of 

 this kind is made in a dry 

 and sheltered position, and 

 the glass covered by light 



shutters of half-inch boards, Fig. 64. SUNKEN PIT. 



it may be used to keep all the hardier class of greenhouse 

 plants, even in localities where the thermometer falls to 

 zero. After all danger of severe weather is past, which, 

 in the latitude of New York, is usually by the last week 

 of April, greenhouses or pits without artificial heat can 

 be safely used for keeping all kinds of greenhouse plants, 

 unless the very tender kinds, such as Coleus, as we rarely 

 have frost sufficiently severe after that date to penetrate 

 into the cold pit or cold greenhouses. In the hands of 

 inexperienced cultivators, plants can always be grown 

 better without artificial heat, which is often very difficult 

 to properly adjust, particularly when the greenhouse is 

 small. 



A new covering for plants has recently come into use, 

 under the name of " Protecting Cloth." It can be bought 

 for eight or ten cents per yard, so that two yards of it 

 tacked to a light frame will make a " sash covering to 

 protect plants, at a cost of twenty-five cents each, which 

 will answer nearly as well as a glass sash, costing ten 

 times :is much, for all protection that plants require 

 after danger of severe freezing is past. Often, during 



