128 
IOWA ACADEMY OP SCIENCE 
TOXICITY OP COCKLEBURS. 
July 20, 1907 . 5 c. c. test tubes used. Growth in mm. 
Ext N 
Ext N-2 
Ext N-4 
Check 
1 1 1 2 
1 
2 
1 
2 
1 
2 
Tst dflv, pxtract 
0 
0 
0 
2 
11 
5 
28 
40 
2d day, distilled water 
0 
0 
0 
0 
17 
20 
30 
38 
August 1, 1907. 
Ext N-8 
Ext N-ie 
Check 
1 
2 
1 
2 
1 
2 
1st day, p-jrtraft 
21 
18 
11 
12 
58 
30 
2d day, distilled water 
26 
20 
23 
27 
52 
30 
This data shows that the extract of normal and half normal strength was 
violently poison, and the N — 4 strength quite so. Considerable of the poison- 
ous effect still remained even when diluted to 1-16 of its original strength. As 
this would bring it down to .08 per cent solid matter in the extract it could 
not be a question of osmosis or even of the toxicity of nutritive salts in the 
extract. 
The toxicity of the burs for clover was also tested by using the following 
modification: Clover seed was sprouted in a large watch glass in tap water 
which was changed once a day. When they were well sprouted, seeds were 
chosen with radicles 5 mm. long and these were transferred to 5 c. c. of the 
solution to be tested, which was placed in a watch glass and the whole covered 
with an evaporating dish to prevent evaporation. The length of the radicles 
was recorded at intervals in mm. The results Were as follows: 
TOXiCITY OP OOCKLEBIUEc? FOR CCOVER. 
Ext N-4 
Ext N-8 
Ext N- 
-16 
Check 
July 31. 
1 
2 
3 
1 
2 
3 
1 
2 
3 
1 
3 
4 
5 
6 
Length at start 
5 
5 
6 
5 
5 
5 
5 
5 
5 
5 
5 
5 
5 
5 
5 
Length August 2 
14 
11 
9 
20 
34 
12 
10 
12 
9 
14 
15 
14 
19 
19 
13 
Length August 5 
25 
15 
36 
20 
18 
40 
22 
* 
28 
23 
21 
17 
25 
25 
ip. A. Loew. The toxic effect of H and OH ions on seedlings of Indian corn. Science 
II 18, pp. 304-308, 1903. 
Dandeno. Relation of mass action to toxicity. Am. .lour. Sci. IV, 17, p. 437, 1904. 
*Dead. 
tAlive. 
