PARAFFINED WIRE POTS FOR SOIL CULTURES. 



65 



as are clay pots (^f the ordinary form. Seeds are then planted in 

 the soil and treated in the usual way (Fig. 10, c). 



It will be observed that the surface of the wire is completely 

 covered with paraffine so that danger of contamination of the soil 

 from the metal of the wire is entirely eliminated. It will also be 

 observed that the surface of contact between the internal soil and 

 the walls of the pot — which really are formed of the same soil 

 cemented into a solid mass b}- paraffin, the wire netting serving 

 now onlv as a support to the otherwise fragile walls — is much less 

 definite than in ordinary pots : for the soil mass continues into the 



T7 



IG. II. 



walls themselves, the only difference between walls and contents 

 Iving in the fact that the spaces which are tilled with air in the 

 latter are filled with solid paraffin in the former. It is this fact 

 upon which the peculiar value of this pot depends, for it avoids 

 the objectionable region of better aeration which occurs in the 

 vicinitv of the walls of other pots. It also avoids the continuous 

 evaporation from the external surface and its possible disturbing 

 effects. 



Where it is desirable to have aeration at the bottom of the pot 

 one or more openings may be made in the wire netting before the 

 soil is placed in position and the paraffin hard-pan and external 

 paraffin layer which afterwards close the openings can be cut away 

 with a knife or other instrument. Wheat seedlings will grow 

 well for six weeks or longer without this aeration. P^or determin- 



