1910] SCHREINER & SKINNER—ABSORPTION AND GROWTH 9 
of the water. After floating this perforated disk on the surface of the 
water, the wheat seed, which has been previously soaked for about 
two hours, not longer, is spread evenly over the surface. This method 
insures an even germination of the seed and has the advantage of 
keeping the seed and later the young seedlings just moist. The seeds 
are never submerged in the water, nor do they remain suspended 
dry above the water. The roots grow through-the holes of the disk 
into the liquid below. This method of sprouting wheat seedlings is 
far superior to growing them in sand, since the seedlings are more 
uniform and the apparatus can be kept sterile much more readily 
than sand. Furthermore, for water culture purposes the seedling 
is readily removed by merely lifting it from the disk. In this way 
the roots or delicate root hairs suffer no injury whatever, while in 
removing seedlings from sand some injury would be unavoidable. 
Moreover, the seedlings are removed direct from water to grow in 
solutions, and thus have the advantage of germinating in a medium 
similar to that in which they are to be grown. 
The water in the germinating pans may be distilled water, if 
desired, or where good tap water can be secured this may be used. 
The water in the pans is changed daily, or, during the warm weather, 
twice a day. Several hundred uniform seedlings can be procured 
from a single disk of the kind described. Whatever inferior plants 
occur are rejected. For the bottle culture work described in this 
bulletin, the seedlings were used when the plumule was about 2 cm. 
high and just ready to emerge from the enveloping sheet. 
More recently disks of perforated aluminum have been used in 
this laboratory and have proven very satisfactory. ‘These disks are 
floated by means of a raft ef sealed glass tubing of such dimensions 
as is required to float the plates in the manner above described. 
Three lengths of tubing 102 cm. long, 35 mm. in diameter, with 
approximately a 1.5 mm. wall thickness, were sufficient to float six 
aluminum disks 30 cm. in diameter and 1.6 mm. in thickness. The 
lengths of sealed tubing and two glass rods 56 cm. long and 12 mm. 
in diameter are wired together into a raft. The entire arrangement 
is floated in a porcelain-lined iron tank. Fig. 2 shows this tank with 
seedlings at various stages of development. 
