1922] GERICKE—ROOT SYSTEMS 205 
Sets of eight containers (Mason jars) of one-half gallon capacity 
were used for each of the different solutions and for each of the 
two different classes of wheat seedlings. These classes of seedlings 
were distinguished by a difference in the extent of root growth 
from that of top growth which the plants had when placed in 
the nutrient solutions. The method employed to obtain seed- 
lings with large root systems was that referred to in the earlier 
paper. This consisted in allowing the cultures to grow in one 
quart Mason jars filled with tap water for five weeks before the cul- 
tures were placed in the nutrient solutions to be tested. The plants 
at this time had a root mass 70-80 cm. long, and had about one-half 
of their total dry matter in the roots. They were transferred from 
the tap water directly to the three nutrient solutions to be tested. 
To grow contemporaneously with these, other seedlings (young 
plants just germinated and therefore having small root systems) 
were set out in other sets of containers filled with the nutrient solu- 
tions to be tested. The seedlings in this latter case were 6-8 cm. 
high, with roots 8-10 cm. long, about 20 per cent of the dry weight 
of the plant thus being roots. Subsequent treatment of all cultures 
was alike, and this included additions of a small amount of FeSO, 
to each culture at regular intervals, also regular additions of distilled 
water to make up the loss of water by transpiration. The test 
period was six weeks. The experiment was carried on in the green- 
house during parts of July and August, the range of temperature 
being 20°-32°C. The relative humidity of the greenhouse did not 
permit excessive transpiration. At the end of the test period, the 
plants were harvested, dried, and weighed. Table I gives the data 
obtained. 
In taking up the data in detail, it may be noted that the cultures 
which had large and extensive roots (class A), when placed in the 
“good” nutrient solution no. 1, produced less than one-half as much 
total dry matter as did the cultures which were started with com- 
paratively small roots (class B). The latter class of cultures at 
the end of the test period had the largest root growth, exceeding by 
more than 76 per cent that of the next largest. The cultures of class 
B are to be considered as normal plants when set out, the other 
class not. Even though class A had by far the larger roots when the 
test was started, it is obvious that these large roots did not operate 
