Wheat ttnder Different Conditions of Growth . 537 
with a waxen appearance. The superphosphate plants were well ahead of 
the unmanured ; the shoots were longer and had commenced to tiller, and 
the root system was much stronger. Each plant showed one thick white 
root over i\ in. in length. At this time the top-dressings of sodium nitrate 
and potassium sulphate were applied, and a fortnight later in all the 
manurial series the ‘white’ roots had become more numerous, and some 
had reached a length of several inches. In many cases they came off from 
the node just above the grain. In the unmanured and in the nitrate series 
the number and average length of the ‘ white ’ roots were very much the 
same, and they remained comparable for the next four weeks, i. e. until 
eleven weeks after sowing. With superphosphate, root growth was 
encouraged from a very early date, and as time went on the differences 
between these plants and the unmanured were accentuated, as is seen by 
comparison of the number of white roots at different periods in the following 
table (I). 
Table I. 
Barley (sown March 5). 
Showing average number of white roots at different dates. 
Age of 
plant. 
Date oj 
observation. 
Unmanured. 
NaNO 3 . 
Su -herb hosbh ate Superphosphate Superphosphate 
0 upei pnommate. + NaNQ ^ + x 2 SO ± . 
Weeks. 
7 
April 20 
3 * 
4 
6 3 
5 
9 
May 4 
7 
4 
15 18 
15 
1 1 
May 18 
17 
T 7 
22 25 
24 
13 
June 8 
0 
0 
0 0 
0 
* Each number is the average of two plants. 
At first the plants with superphosphate and nitrate gave lower 
numbers of white roots than did the superphosphate alone, but later the 
former drew ahead. With superphosphate and potash the numbers were 
much the same as with the superphosphate alone (see Table I). The length 
reached by the white roots did not seem to be affected by the type of 
manuring, but ranged up to about 9 in., according to the age of the roots. 
These white roots do not retain their unbranched character throughout 
the life of the plant, but after some time they put out laterals and 
ultimately approximate to the general root system. When all the plants 
were eleven weeks old, a marked change was noticed in the formation of 
the root system. The thick white unbranched roots were no longer present, 
though a certain number of short roots occurred which were thin and 
showed incipient laterals. With the superphosphate and nitrate manuring 
a few thick white roots were still noticeable, all of which carried laterals 
well down their length, while with the superphosphate and potash a good 
number of long, thick, white roots with a number of laterals in the upper 
4 in. were noticed. From this time onwards the ‘white’ roots entirely 
