EFFECT OF DEFINITE QUANTITIES OF MOISTURE. 43 



no water was added. However, a temperature of 40 C. is sufficient 

 to injure many seeds, even though the liberated water be permitted to 

 escape, as is shown in the tests of the onion, No. 1539 of the table. 

 The greatest injury when air-dried seeds are sealed in bottles and then 

 subjected to a higher temperature is due to the increased humidity of 

 the confined air, as a result of the water liberated from the seeds. 



At first glance some of the conditions given ih the above table may 

 seem to be extreme and far beyond any normal conditions that would 

 be encountered in the ordinary handling of seeds. This may seem to 

 be especially true with the seeds kept in the bottles with 3 cc. of 

 water where the additional amount of moisture absorbed gave rise, in 

 some of the seeds, to a water content of approximate!} 7 20 per cent. 

 Yet this need not be thought of as an exception, for such extreme 

 cases are often encountered in the commercial handling of seeds. 

 During the process of curing even more drastic treatment is not 

 infrequently met with. Pieters and Brown 05 have shown that the 

 common methods emplo}^ed in the harvesting and curing of Poapra- 

 tensis L. were such that the interior of the ricks reached a tempera- 

 ture of 130 to 140 F. (54.4 to 60 C.) in less than sixteen hours, at 

 which temperature the vitality of the seed is greatly damaged and 

 frequently entirely destroyed. The interior of one rick reached a 

 temperature of 148 F. (64.4 C.) in twenty hours, and the vitality 

 had decreased from 91 per cent to 3 per cent, as shown by the ger- 

 mination of samples taken simultaneously from the top and from the 

 inside of the same rick. 



On the other hand, the extreme cases need not be considered. 

 Take, for example, the onion seed that was sealed in a bottle with 

 1 cc. of water and maintained at a temperature of 37 to 40 C. The 

 increase in weight due to the water absorbed was 3.91 per cent, thus 

 giving a moisture content of 11.2 per cent and a complete destruction 

 of vitality. The cabbage seed, kept in the same bottle, had absorbed 

 a quantity of water equivalent to 2.35 per cent of its original weight, 

 which, with the 5.90 per cent contained in the original sample, gave 

 8.25 per cent of water. This sample of seed germinated only 11 per 

 cent, having thus no economic value. In neither of these samples 

 was the amount of water present in the seeds greater than that ordi- 

 narily found in commercial samples. Moreover, the temperature was 

 much below that frequently met with in -places where seeds are 

 offered for sale and likewise well within the limits of the maximum 

 temperature of our summer months, especially in the Southern 

 States. Take, by way of comparison, the maximum temperatures of 

 some of the places at which seeds were stored to determine the effect 

 of climate on vitality, as shown in another part of this paper. During 



"Bulletin 19, Bureau of Plant Industry, U. S. Department of Agriculture, 1902. 



