EFFECT OF DEFINITE QUANTITIES OF MOISTURE. 41 



for in that way. On the other hand, it is quite probable that a por- 

 tion of the increase in weight Was due to the results of intramolecular 

 transformations and to the coexistent respiratory activities of the 

 seed. The means of making these determinations are far from easy. 

 Van Tieghem and G. Bonnier have shown a that seeds kept in sealed 

 tubes in atmospheric air increased in weight during two years, but the 

 increase was very small. In their experiments the peas which were 

 in scaled tul >os i ncreased T -j ^ of their original weight. A corresponding 

 sample kept in the open air increased T V of its original weight. 



Nos. 154:0 to 1545 in Table X show an increased weight in seeds 

 when sealed in bottles for TO days. These seeds were previously 

 dried for 30 days at a temperature of 30 to 32 C. Disregarding the 

 increase in weights as above given and the factors to which such 

 increase may be attributed, it is quite evident that in all cases where 

 water was added the increase in weight was due chiefly to the absorp- 

 tion of the water. The absolute increase was approximately the same 

 as the weight of the water added. 



The amount of water absorbed by different seeds varies greatly 

 under identical conditions, depending largely upon the nature of the 

 seed coats and the composition of the seed. The average increase in 

 weight of the seeds used in these experiments was as follows: Onion, 

 6.27 per cent; pea, 5.51 per cent; cabbage, 4.12 percent; lettuce, 3.99 

 per cent; tomato, 3.99 per cent. The loss in vitality of the corre- 

 sponding samples was 28, 12, 23.7, 18.5, and 14.7 per cent, respec- 

 tively. The relationship here is quite close, the amount of water 

 absorbed being roughly proportional to the loss in vitality. The 

 peas, however, afford an exception to this general statement. But it 

 must be remembered that peas require a much larger percentage of 

 moisture to start germination and are likewise capable of undergoing 

 much wider variations than the other seeds in question. However, 

 before a definite ratio can be established between the absorption of 

 water and the loss in vitality, many other factors must be taken into 

 consideration, such as the composition, water content, and duration of 

 vitality of the seed under natural conditions. 



Another interesting factor is shown in No. 1546 of Table X. These 

 soods were dried for 30 days at a temperature of 30 to 32 C., after 

 which they were kept in an open bottle in the laboratory for 40 days. 

 During the 30 days' drying the cabbage lost 2.41 percent, lettuce 2.59 

 per cent, tomato 2.71 per cent, and the onion 3.47 per cent of moisture. 

 These same seeds when exposed to the free air of the laboratory for 40 

 days never regained their original weight, the increase being as follows: 

 Cabbage, 0.6 per cent; lettuce, 0.58 per cent; tomato, 1.56 per cent; 

 onion, 0.89 per cent. The average quantity of water expelled was 2.79 



Bul. S.x-. hot. I<>:in<-<, 29: 25-29, 149-153, 1882. 



