6 BULLETIN 1120, U. S. DEPARTMENT OF AGRICULTURE. 
10 a. m. to 4 p. m. This typical arrangement of plats is represented 
diagrammatically in Figure 1. 
Experimental plats of the kind described were sown at Fargo on 
May 22 (plat A), June 9 (plat B), June 27 (plat C), and July 18 
(plat D) . In plat A the shades unfortunately were not put in position 
until after canker had occurred. Canker occurred in plat A, not in 
plat B, to a slight extent in plat C, and not in plat D. Similar 
plats were sown at Mandan, N. Dak., on April 28, June 11, and July 1, 
except that where sand was applied at Fargo the soil was compacted 
at Mandan. Dry weather, cutworms, and grasshoppers made the 
results at Mandan unworthy of consideration. 
While the canvas shades unfortunately were not put in position 
in plat A at Fargo until after canker had occurred on June 16, the 
presence and absence of weeds in different parts of the plat served 
much the same purpose in varying the amount of shade. Rows 1, 
2, and 3 had been carefully weeded, while the rest of the plat was 
rather weedy. It was at once strikingly evident that by far the 
most canker occurred where the young flax plants had not been shaded 
by weeds or by the nurse crops. The data from this experiment 
are given in Table 2, showing a summary and comparison of the 
percentages of canker under different conditions. 
Table 2. — Results of experiments conducted at Fargo, N. Dak., to determine the effect 
of various types of shading of flax in sanded and unsanded ground on plat A, sown on 
May 22, 1919. 
[Data on the occurrence of heat canker of flax recorded on June 18, 1919.] 
Without sand on surface. 
Surfaced with sand. 
Num- 
ber of 
plants 
in row. 
Plants cankered. 
Num- 
ber of 
plants 
in row. 
Plants cankered. 
Conditions as to shading. 
Num- 
ber. 
Per cent. 
Num- 
ber. 
Per cent. 
Actual. 
Aver- 
age. 
Actual. 
Aver- 
age. 
No shade: 
Row No. 1 
469 
411 
188 
329 
461 
361 
355 
147 
189 
308 
637 
352 
390 
379 
322 
396 
348 
216 
46.0 1 
f 480 
467 
277 
f 574 
433 
198 
159 
80 
288 
115 
f 333 
482 
407 
236 
188 
119 
118 
179 
80 
21 
18 
17 
10 
6 
2 
7 
4 

19 
2 
1 
6 
5 
1 
37.3 
17.1 
7.6 
3.1 
4.0 
5.1 
3.8 
2.5 
2.4 
3.5 

4.0 
. 5 
.4 
3.2 
4.2 
.9 
Row No. 2 
168 40.9 1- 41.4 
70 37.2 1 
i 20.5 
Row No. 3 
Shaded by weeds: 
Row No. 4 
34 10. 3 
7.3 
4.3 
Row No. 5 
34 
25 
10 
10 
33 
5 
19 
16 
10 
11 
40 
9 
8 
7.4! 
6.9 ' 
2.8 ! 
6.8 
17.5 t 
1.6 
3.0 
4.5 
2.6 i 
2.9 ' 
12.4 
2.3 
2.3 
Row No. 6 
Row No. 7 
i 3.5 
Row N o. 8 
Row No. 9 
Row No. 10 
Shaded by weeds and grain: 
Row No. 11 
Row No. 12 
Row No. 13 
Row No. 14 
1.9 
Row No. 15 
Row No. 16 
Row No. 17 
