PLANT PITS. 



'35 



ventilators widely to lower the temperature. This cannot be done without injury. 

 Early and steadily increasing ventilation during bright mornings, to enable the tem- 

 perature inside the house to rise in the same steady, natural manner as it does outside, 

 is a golden rule to remember in the ventilation of greenhouses and other garden 

 structures. Early closing is also very desirable, under certain conditions that will be 

 subsequently pointed out. Only when the air is soft and genial should it be admitted 

 in any large volume through the front sashes ; and the easy mode of ventilation by 

 opening the doors and leaving them open, is only permissible during sultry weather. 



Pits. 



When the term "pit" is used in gardening, it is generally understood to mean a 

 low, comparatively flat-roofed structure with permanent brick or stone sides and ends, 

 the roof consisting of bearers and movable glazed sashes after the manner of the old 

 glazed portable frames. Former generations of gardeners turned these pits to good 

 account in plant culture; but, unless heated by hot water, more than ordinary care has 

 to be taken in protecting the occupants from severe frost. That is the reason why low 

 span-roofed and lean-to houses without glazed sides, and frequently designated pits, 

 are becoming so common. The sides and sometimes the ends of these low pit-houses 

 are usually of brickwork, with the path in the centre sunk 2 feet below the ordinary 

 ground level. A very handy form of plant pit is shown at a, Fig. 64, page 130. Fifty-four 

 inches is a good width for these economically constructed pits. If made much wider 

 the occupants are not so easily reached at the back as is desirable. The lights or sashes 

 may either be hinged and propped open as required by the ratchet arrangement shown, 

 or they can be made to take off as in frames, air being admitted by either blocking them 

 up in front or at the sides, or by drawing them down slightly or considerably according 

 to the weather. There are fewer breakages with the fixed lights, but, on the other- 

 hand, front ventilation is not always good for the plants. If box frames and sliding 

 shutters are built into the wall between the pit and house to which it is attached, at a 

 distance of about 2 feet apart, these, when open, answer the double purpose of 

 admitting fresh yet not very cold air to the greenhouse, and at other times of warm 

 air circulating from the house into the frames, a heavy covering of mats on the glass 

 then sufficing to exclude frosts. A single hot-water pipe branching from the flow pipe 

 in the greenhouse, taken along the front of the pit, then conducted into the greenhouse 

 pipe at the other end of the pit, adds considerably to its usefulness. 



