274 
IOWA ACADEMY OF SCIENCE Voe. XXIX, 1922 
TABLE i 
TIME AT WHICH THE WHEAT AND OATS PLANTS ACQUIRE 
THEIR MAXIMUM VALUES 
Culture 
Maximum 
EEAE AREA 
Maximum 
Maximum rate oe 
CerEae 
Mustard 
Transpiration 
Transpiration 
Wheat 
No. 1 
March 30 
April 11 
May 21 
No. 2 
April 11 
April 6 
April 16 
May 21 
No. 3 
March 16 
March 
March 16 
May 21 
No. 4 
April 6 
February 16 
March, 18 
May 25 
WalD 
No. 5 
April 20 
May 21 
May 25 
No. 6 
April 28 
February 16 
May 21 
May 25 
N p. 7 
March 30 
March 
March 19 
May 21 
No. 8 
April 6 
February 9 
April 11 
May 21 
The extent to which a weed like mustard will use up water and 
compete with a crop in which it is grown is shown in Table 2 
taken from the same series as is recorded in Table 1. 
TABLE 2 
HEIGHT, DRY WEIGHT AND AMOUNT OF WATER TRAN- 
SPIRED BY WHEAT WITH MUSTARD, OATS AND OATS WITH 
MUSTARD CULTURES, FOR A GROWING SEASON 
CUETURE 
Maximum Height 
Dry Weight 
Transpiration 
Cereae 
Mustard 
Wheat 
No. 1 
110 cm. 
127.80 gm. 
53.30 kgm. 
No. 2 
109 cm. 
66 cm. 
91.61 gm. 
54.56 kgm. 
No. 3 
86 cm. 
68.10 gm. 
33.66 kgm. 
No. 4 
90 cm. 
31 cm. 
57.95 gm. 
33.86 kgm. 
Oats 
No. 5 
80 cm. 
117.95 gm. 
47.58 kgm. 
No. 6 
73 cm. 
7 cm. 
60.30 gm. 
48.55 kgm. 
No. 7 
62 cm. 
60.30 gm. 
31.11 kgm. 
No. 8 
68 cm. 
15 cm. 
52.38 gm. 
28.34 kgm. 
In this table, comparison cannot be made between the wheat 
series and the oats series indiscriminately, for cultures 3, 4, 7 and 
8 have too many plants and consequently there was a competition 
between the members of the same variety. Inasmuch as the 
same number of plants were not used, comparison can be made 
only between each pair in the order given. 
It is noticed that there is not a material difference in the height 
of the wheat and oats plants. In the wheat series, the mustard 
plants attain a greater height than in the oats series. This sug- 
gests immediately that the oats is a better plant than wheat to use 
in the elimination process for the eradication of a weed like mus- 
tard. The oats series also show that it is disadvantageous to place 
