FIBER PLANTS 407 



unevenly scattered throughout the field and escape notice 

 until late in the season. 



If the weather favor the disease, each new area of infec- 

 tion may increase sufficiently to reach plants in several 

 adjacent drill rows. These infection areas are nearly 

 always circular, and enlarge each year that flax is grown 

 thereon. A diseased spot 1-2 m. in diameter the first 

 year may become 2-3 m. the second year. Thus only 

 a few years are required for the disease to gain complete 

 possession of a field. The disease not only persists in a 

 field not sown to flax, but the disease areas may even en- 

 large when no flax is present. When soil is once infected, 

 no way is known to render it suitable for flax again. 



This is essentially a soil disease, and it is spread in the 

 ways suggested under soil diseases, notably by soil particles, 

 drainage water, and especially diseased flax straw which 

 may get into the manure. The chief agent of dissemina- 

 tion, however, is the seed. In threshing, the spores of the 

 causal fungus, which are abundant upon the dead straw, 

 find lodgment upon the seed, especially if it be moist. 



To prevent carrying the disease to land yet uninfected, 

 all seed should be disinfected in the folloAving manner : — 



Use formaldehyde at the rate of 1 pound to 40 

 or 45 gallons of water. Spread the seed upon a tight 

 floor or upon a canvas and sprinkle or spray upon it 

 a small amount of the liquid. Shovel, hoe, or rake the 

 grain over rapidly. Repeat this sprajnng, shoveling, and 

 raking until all of the seeds are evenly moistened, yet not 

 wet enough to mat or gum together. Continue to stir the 

 grain, so that the mass may become dry as soon as possible. 

 Avoid any excess of moisture. If flax seeds are dipped 



