86 GREENHOUSE CONSTRUCTION AND HEATING. 
required to make the solid beds referred to above, unless 
of course, the house is partly sunk, when the soil taken 
out of the pathway will yo a good way towards it. 
But except for bedding plants, etc., such sunk houses 
are not now considered desirable, so that unless there 
is plenty of rough materials of some kind at hand it 
becomes necessary to employ raised stages. Solid beds 
must be surfaced with 3in. or 4in. of moderately fine 
ashes, to prevent worms entering the pots. Most pot 
plants thrive better on such a solid ash-bed than elsewhere, 
especially in hot weather, when the cool, moist bottom 
is very grateful to the plants. Pots standing on an open 
or lath staging directly over two or more rows of hot 
pipes also become dry very quickly, and unless frequently 
attended to with water, are very liable to suffer from 
extreme drought. In nearly all such cases the staging 
should be a close or impervious one, especially if the 
pipes are at all near the staging. 
Raised stagings may be constructed in several ways, 
and of various materials. The old-fashioned style was 
to use narrow battens, or stout laths, about Qin. by lin. 
in section, nailed down to wooden joists let into the wall 
at the back, and supported by a post or upright, also of 
wood, in front. A space of nearly an inch was allowed 
between each pair of battens, in order to allow of any 
surplus water passing freely away from the pots, and 
also of a free current of air passing between the plants. 
As already seen, this plan suits pelargoniums and some 
other plants growing in a cool temperature, but when 
there are hot water pipes immediately beneath, the pots 
are liable to suffer seriously from drought. 
