1913] HOFFMANN—PARAFFIN BLOCKS FOR GROWING SEEDLINGS 247 
using a piece of ordinary glass tubing which has been drawn out in 
a conical form. By pushing this through the paraffin a perforation 
is secured which is larger at the top and smaller at the bottom of the 
block, and which will prevent the seed from falling through into 
the liquid in which the paraffin blocks are to be suspended. In this 
manner one can make a support of any size and with as many per- 
forations as desired. These blocks when placed in the liquid 
culture medium serve automatically to keep the roots immersed 
‘IG. 3.—Same seedlings as in fig. 2, but removed from water; far less differentia- 
tion in root dev elopment is evident. 
in the liquid, since they are free to rise and fall with variations in 
the level of the nutrient solution. This is impossible with a cork 
which fits snugly in the neck of the vessel, unless one continually 
restores the water lost by transpiration and evaporation. 
The size of the block, as well as the perforations, will depend 
entirely upon the seedlings to be grown, making them large for 
peas and corn, and small for wheat and clover. The blocks thus 
Prepared can be floated upon the culture medium in which the 
seedlings are to be grown, and, as already stated, will rise and fall 
