248 BOTANICAL GAZETTE [MARCH 
with changes in the elevation of the nutrient solution. Sufficient 
bulk must be given to the blocks to provide for the increased 
weight resulting from the growth of the plant. 
The most suitable receptacle for floating these block cultures 
has been found in the form of an ordinary hydrometer cylinder 
which has the enlargement at the upper portion of the cylinder. 
This is well shown in the accompanying illustration (fig. 1). 
For photographic purposes of seedlings thus grown these floats 
with their burden are placed in large, flat, glass vessels similar to 
the rectangular museum jars which are now being employed. In 
this way the root systems are well distributed and give a photograph 
revealing any differences which may exist in the root development. 
A comparison of the two photographs submitted (figs. 2 and 3), the 
one taken as above described, the other after removal from the 
water demonstrates this feature very strikingly, and proves the 
advantages of photographing as described. This method of photo- 
graphing is considered worthy of employment where work of a 
similar nature is performed and presented. 
AGRICULTURAL BACTERIOLOGICAL LABORATORIES 
UNIVERSITY OF Wisconsin, Mapison, WIS. 
