228 



Journal of Agricultural Research 



Vol. XX, No. 3 



tests were so variable that accurate comparisons of growth can not be 

 made. However, the graph, in its similarity to the germination graphs, 

 illustrates the close correlation between viability of the sample and the 

 retardation of seedling growth. Being an average of the two experi- 

 ments, it brings the maximum growth retardation to 60 per cent. 



Since the relation between degree of seed injury and the moisture 

 content of the atmosphere in which the seed was stored had been shown, 

 it was surmised that a similar correlation could be shown to exist be- 

 tween humidity and the formation of paraformaldehyde. After the 

 seed samples of the first experiment were removed from the desiccators, 

 a Syracuse watch glass containing 10 cc. of commercial formaldehyde 

 solution was placed in each. The solid polymer first appeared after 



three days as a white suspen- 

 sion in the dishes in humidities 

 of 20 and 10 per cent, and in 

 the very dry atmosphere over 

 concentrated acid. Two davs 

 later only the dry, white solid 

 was left in these dishes, and a 

 white precipitate made the 

 solutions opaque in the 30, 

 40, and 50 per cent atmos- 

 pheric humidities. The den- 

 sity of the suspensions was in 

 inverse proportion to the hu- 

 midity in these desiccators. 

 Xot until 10 days had passed 

 did any paraformaldehyde ap- 

 pear in the 60 per cent hu- 

 midity, at which time all that formed earlier in the dishes in the dryer 

 atmospheres was dry. No sign of the white solid ever appeared in the 

 more humid desiccators, although the solution in 70 per cent eventually 

 evaporated to dryness (PI. 38, B). It was very interesting thus to find 

 that the highest humidity permitting the formation of paraformaldehyde 

 was also the highest in which seed injury occurred after treatment with 

 the 0.1 per cent solution of formaldehyde — that is, the germination of 

 wheat was lowered in the same desiccators in which paraformaldehyde' 

 formed upon the evaporation of formaldehyde solutions in them. 



Again, at the end of the second experiment, after the wheat was re- 

 moved from the desiccators, dishes containing equal quantities of un- 

 diluted formaldehyde solutions were placed over the sulphuric acid 

 dilutions, and the appearance and rapidity of formation of paraformal- 

 dehyde were noted. In this case 5-cc. instead of 10-cc. quantities were 

 used. After two days, the first white suspension appeared in the desic- 



Fig. 3. — Graph showing the relation of humidity of the air 

 to percentage of germination of stored seed in second 

 experiment. 



