HEAT CANKEK OF ELAX. 
FIELD EXPERIMENTS. 
During the latter part of the season of 1917 a shading experiment 
was conducted. The shade was provided by two pieces of canvas, 
each about 6 feet square, stretched horizontally about 3 feet from 
the ground above the young flax plants. In this experiment canker 
occurred in neither the shaded nor the unshaded area. However, 
the experiment did show that methods of shading which would 
reduce the light to a less degree were desirable. These investigations 
were temporarily discontinued during 1918. 
In 1919 further experiments were planned and conducted to test 
the effect on young flax plants of intense sunlight and resulting heat 
at the soil line. Experiments were conducted also with a view to 
producing flax canker by artificial means. 
Shading experiments were planned in which partial shade was 
provided by (1) strips of canvas, (2) cereal nurse crops, and (3) 
weeds. In these shading experiments the typical plat (Fig. 1) was 2 
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Fig. 1.— Plan of a typical plat in field experiments conducted at Fargo, N. Dak., in 1919, to determine 
the cause of flax canker of the nonparasitic type. Pwows 3 and 8, marked with an asterisk (*), sown 
thinly at half the normal rate. Canvas strips 10 inches wide and 1 rod long were placed close to the flax 
rows marked with two asterisks (**) for shading from about 10 a. m. to 4 p. m., half on sanded area 
half on area not sanded. 
rods long east and west and 10 feet wide north and south. It was 
divided into halves by a line extending north and south, and the soil 
of one of these halves was covered thinly with sand. The plat con- 
sisted of five rows each of two varieties of flax. North Dakota Resist- 
ant No. 114 (C. I. 13), a wilt-resistant variety, and Reserve (C. I. 19), 
a variety susceptible to wilt, and two rows each of flax with one of 
the cereals, oats, barley, spring wheat, or winter wheat, as a nurse 
crop. The rows extended east and west, so that each plant would be 
exposed to the sun's rays during the hottest part of the day and for 
the longest period possible. There was a 12-inch space between the 
second and third rows of each variety, and the third row of each 
variety was sown at half the usual rate. The other rows were spaced 
6 inches apart. Half of the second row of each variety was shaded by 
placing just south of it vertical strip of canvas 10 inches wide and 1 
rod long. By this meai "^ the young plants were shaded from about 
