368 Journal of Agricultural Research voi.xix.no.s 



the short 2-hour treatment shows more injury than a longer treat- 

 ment; with barley, 14 out of 19 tests show more injury from the short 

 treatment; and so with oats in 29 out of 41 tests and with rye in 2 out 

 of 3 tests. In some cases there is a steady decrease of injury as the treat- 

 ment period lengthens. 



A study of the tables given by Stuart (p) in his paper on the effect of 

 formalin on oat germination shows almost invariably greater injury 

 to germination caused by 2-hour treatment than by 4-hour treatment of 

 seeds, and a similar effect on the final yield of grain and straw — a fact 

 not commented on by that writer. 



These facts led to the conjecture that the formaldehyde content in 

 the seeds at the end of 3 hours was really stronger than in the 12-hour 

 treated seeds. Such a condition might be explained by the hypothesis 

 that the dry seeds absorb the formaldehyde itself more rapidly than 

 they do the water and that by diffusion later this is diluted to a strength 

 more like the original solution through continued absorption of water by 

 the cell walls and cells. 



Theoretically, therefore, if the 3-hour treatment could be made in 

 such a way that the final solution content of the seeds would be com- 

 parable in amount and dilution with that finally present in 12-hour 

 treated seeds, the effects on germination should also be similar. By 

 impregnating the cell v.^alls and cells of dry seeds with water and then 

 treating with formalin for three hours, it appeared as if this result might 

 be attained; for, in accordance with the lavs^s of diffusion of dissolved 

 substances, the formalin should be diluted as it diffused into the water- 

 saturated seed tissues. 



Acting on this hypothesis, wheat seeds were first soaked in tap water 

 for 10 minutes, drained, and kept moist for 9 hours, then soaked thorough- 

 ly in formalin i to 400 for 10 minutes, drained, and kept moist for 3 hours 

 in order that the water absorbed during the first 9 hours might weaken the 

 full strength solution diffusing into the cells during the next 3 hours and 

 might result in less injury than was caused by the 3-hour treatment of 

 dry seeds. Following this, numerous experiments were made, varying 

 the length of time during which the seeds were kept moist but starting 

 out always with a preliminary short plunge into water. This method — 

 short exposure under water followed by varying lengths of exposure to 

 moist air (covered) — has been designated throughout this paper as the 

 "presoak" method of seed treatment. In the same way, whenever 

 exposure to formalin is mentioned it means always that the seeds were 

 plunged into the formalin water solution for a short period only (usually 

 10 minutes) and then kept moist (covered) for the designated number of 

 hours. 



The seeds of two varieties so treated were planted in the greenhouse 

 with 12-hour treated seeds and controls. Table III records the results 

 observed. 



