July, 1922] GERICKE — ■ ROOT DEVELOPMENT AND TILLERING 
extent of the root development of a plant to the extent of its top, when 
grown under different sets of conditions, has not been sufficiently studied. 
Especially is this true in soil cultures, where it is difficult to make exact 
determinations. It is conceivable that the kind of root development a 
plant may have when a treatment such as an application of nitrogen is 
made to it may be a very important factor that affects materially the 
nature of the subsequent responses of the plant. 
In order to obtain data as to what effect differences in the extent of 
root development of wheat seedlings would have upon the tillering of the 
plants when grown in the same nutrient solutions, the following experiment 
with water cultures was carried out: Wheat seedlings 8 to 10 centimeters 
high, having roots 10 to 12 centimeters long, were set up according to 
the usual method employed for solution-culture investigations, and were 
grown for 25 days in two-quart containers filled with tap water from the 
laboratory. At the end of this period, the seedlings had developed a very 
extensive root system. Roots from 50 to 70 centimeters long had formed 
while the tops had grown only a little, attaining a height of approximately 
10 to 12 centimeters. Sets of these cultures with large root development 
were then transferred, respectively, to several different kinds of complete 
nutrient solutions. At the time these several sets were placed in the 
nutrient solutions, other sets of wheat seedlings a few days old having 
shoots 8 to 10 centimeters high and a comparatively small root develop- 
ment, viz., roots about 10 to 12 centimeters long (similar to those used 
for the tap-water series), were set up to serve as controls, being placed 
in similar nutrient solutions to those in which were placed the sets of 
large root development. The investigation, therefore, as planned, con- 
cerned itself with a study of some of the effects the same kind of nutrient 
solution would have upon Wheat seedlings of different root development, 
some having a large root development and others a comparatively small 
root development at the time the cultures were placed in the nutrient 
solutions. In one class of cultures, practically one half of the total dry 
weight was contained in the roots, while in the other class about one fourth 
of the total dry matter was roots. The roots of the cultures grown in 
tap water for 25 days were from four to five times as long as their tops. 
The lengths of the roots of the plants not so treated were only a little 
greater than those of their tops. The weight of the tops of the two sets 
of cultures was about the same, but the weight of the roots in the one 
was about four times the weight of the other. Subsequent treatment of 
these two classes of cultures was the same throughout the test period 
employed. The data in table i are given as an example of the results 
obtained : 
