4 TOXIC SUBSTANCE EXCRETED BY PLANTS. 
In all cases the results given are the mean of a large num- 
ber of observations. 
Observation (1) is the nearest approach possible under the 
conditions of the experiment, to the yield of a crop when grown 
isolated, 7.e., influenced neither by plants of the same nor of other 
species. In the present season it is hoped to obtain a nearer 
approximation. 
The results obtained (1906-07) are given in the table follow- 
ing, the total yield per acre (dry weight) of the crops being given 
in Ibs, :— 
TABLE I. 
YIELD (fruit and vegetative portion) in lbs. per acre of the crops 
CROPS (of which yield is given.) in first column when grown bordering on a plot of : 
Fallow. Sorghum. | Cajanus. | Cotton, Sesamum, 
Sorghum ... sy sts 10,735 4,830 8,051 8,802 8,158 
Cajanus_ ... a 4,633 694 1,621 1,621 2,409 
Cotton... a is 3,817 229 763 1,145 1,259 
Sesamunm ... an - 1,650 Nil 198 247 643 
| 
Taking the yield next to the fallow as a rough approximation to 
the yield of the isolated crop, we get the following percentage 
reduction in these yields produced by a neighbouring plot® of 
another crop : 
TABLE IL. 
CROPS (of which percentage decrease | Percentage DECREASE in yields of crops in first column 
is given). when grown near 
| Sorghum. Cajanus, . Cotton. | Sesamum. 
Sorghum : 7” a 55 26 18 _ 24 
Cajanus ee a at . 85 2 a. 165... 48 
Cotton oe he a F i oF eae 80 70 67 
Sesamum | 100 88 85 61} 
* In the present season observations will be made on the yield of crops when a row is 
bordered on both sides by another crop. 
| Since sesamum is extremely sensitive to the presence in its vicinity of other plants whether 
of the same or other species, the yield next to fallow (Table IT) is probably lower than the isolated 
yield by a much greater extent than in the case of all other crops, since the latter are less 
sensitive. The figures in the bottom line of Table II should therefore all be increased. 
+ This is the result of one observation only and is probably too high since sesamum will 
not grow at all within 2ft. (the width of the rows) of sorghum. 
