212 BOTANICAL GAZETTE [MARCH 
2. The proper amount of water to be added to the air-dried soil 
is dependent upon the soil texture, varying from 5 per cent for sand 
to 30 per cent for clay. The amount to be used is best determined 
by adding water slowly from a graduate to a small weighed portion 
of soil until a condition of good tilth is reached. A heavy soil can 
be moistened without puddling by placing it on a slab or table in 
a cone-shaped pile, with a large crater in the top, into which the 
required amount of water is slowly poured. The crater is then 
filled with dry soil from the sides, and the whole mass is covered 
to prevent evaporation, and allowed to stand over night, or pref- 
erably longer. The soil is then thoroughly mixed, during which 
process it is sifted through a coarse screen (3 inch mesh). Any 
pellets of soil having more than their proportionate amount of 
water will be removed in this way. After mixing, the moist soil 
should be kept in a tight receptacle until ready for use. 
Impervious pots of course must be used in order to prevent 
the soil in contact with the pots from drying out below the minimum 
of available soil moisture. We have found that ordinary straight- 
walled drinking glasses form very satisfactory pots for this work. 
During the process of filling the glasses, the soil is slightly com- 
pacted by jarring the bottom of the glass against the hand. Three 
to five seeds are planted in each pot, about 1 cm. in depth, after 
which the surface is smoothed and compacted slightly. The soil 
surface after planting should be about 1 cm. below the edge of the 
glass. It is sometimes advantageous to plant seeds which have 
just begun to germinate; this insures a uniform stand, and avoids- 
excessive respiration below the wax seal. : 
3. Insealing the pots the wax is heated slightly above the melting 
point, and a sufficient amount is poured into the pot to cover the 
soil surface about 3 mm. in depth. The pot is rocked slightly $° 
as to bring the wax into thorough contact with the inner walls of 
the pot, after which the excess wax is poured off. If the wax 1S 
at the proper temperature, this will give a perfect uniform seal over 
the entire surface. If the seal is not perfect, the process is repeated. 
The wax layer should be approximately 1 mm. in thickness, and 
should be in close contact with the soil. If the wax does not adhere 
to the soil surface, the pots should be resealed, since the plants may 
buckle under the wax cover if it is not adherent. 
