PLATE 38 



A. — Wheat seedlings showing injury produced by allowing the seed to lie in dry 

 soil for 30 days after treatment with a 0.1 per cent solution of formaldehyde: Left, 

 control, dipped in water, 100 per cent germination; center, dipped in 1 to 320 (0.1 

 per cent) formaldehyde, 62 per cent germination; right, dipped in 1 to 160 (0.2 per 

 cent) formaldehyde, 48 per cent germination. 



B. — Desiccators with different degrees of atmospheric humidity obtained by the 

 use of mixtures of sulphuric acid and water in different proportions. The dishes 

 containing formaldehyde were not placed in the desiccators until after the degree of 

 injury to the treated seeds had been determined. The atmospheric humidities were as 

 follows: No. 1, saturated; No. 2, 90 per cent; No. 3, 80 per cent; No. 4, 70 per cent; 

 No. 5, 60 per cent; No. 6, 50 per cent; No. 7, 40 per cent; No. 8, 30 per cent; No. 9, 

 20 per cent; No. 10, 10 per cent; while No. 11 was absolutely dry, over undiluted 

 acid. Note the white paraformaldehyde formed in these dishes in the drier cham- 

 bers, beginning with No. 5. (See Table VII for specific gravity readings of sulphuric 

 acid and water mixtures.) 



