36 THE VITALITY AND GERMLNATION OF SEEDS. 



THE EFFECT OF DEFINITE aUANTITIES OF MOISTURE ON THE 

 VITALITY OF SEEDS WHEN THEY ARE KEPT WITHIN CERTAIN 

 KNOWN LIMITS OF TEMPERATURE. 



The results of the experiments just discussed furnish a fair criterion 

 by which to judge the vitality of seeds when influenced by tempera- 

 ture and moisture. It was still necessary to determine the efl^^ect of 

 definite quantities of moisture on the vitality of seeds when they are 

 submitted to temperatures well within the limits of that which may 

 be encountered in commercial transactions. 



On December 19, 1900, preparations were made to determine these 

 factors. Seeds of cabbage, lettuce, onion, tomato, and peas were used 

 for these experiments, which continued for 70 or 72 days. All of this 

 seed was of the harvest of 18*J9 and had been in the laboratory during 

 the eleven months immediately preceding the setting up of the experi- 

 ments, being thus thoroughly air-dried. The amount of moisture 

 present in the seeds at this time, as indicated by drying at 100"^ C, 

 was as follows: Cabbage, 5.90 per cent; lettuce, 5 per cent; onion, 6.4:1 

 per cent; tomato, 1.71 per cent, and peas, 8.41 per cent. 



The preparations were made as follows: 



{a) Air-dried seeds were placed in bottles of 125 cc. capacity. The 

 bottles were closed with cotton plugs in order to protect the seeds 

 from dust while permitting a free circulation of air. This set served 

 largelj^ as a check. 



{h) Air-dried seedb were carefully weighed and then put into 125 cc. 

 bottles, closed with firm corks, and sealed with paraffin. 



(c, d, e, and /") These samples were also carefully weighed and 

 sealed in bottles as J, but in the difl'erent series of bottles there was 

 first introduced 0.5, 1, 2, and 3 cc. of water which had been previously 

 absorbed l)y small strips of filter paper. 



{(/) The seeds constituting this series were first dried for 30 daj^s at 

 a temperature of from 30^ to 32° C. and then put up in bottles which 

 were sealed with paraflin. The loss in weight as a result of the dry- 

 ing was as follows: Cabbage, 2.11 per cent; lettuce, 2.59 per cent; 

 tomato, 2.71 per cent, and onion, 3.17 per cent, leaving a water con- 

 tent of onl}^ 3.19 per cent, 2.11 per cent, 2 per cent, and 2.91 per cent, 

 respectively. (Peas were not included in this series.) 



One of each of the above preparations was then subjected to difl'erent 

 degrees of temperature as follows: 



(1) Outdoor conditions, protected from rain and snow, but freely 

 subject to all changes in temperature and humidity. The temperature 

 during the time of the experiment, December 19, 1900, to February 28, 

 1901, varied from a minimum of —21.6" C. to a maximum of 8.9" C. 



(2) In a fruit cellar having u comparatively low and uniform 

 temperature ranging from 10" to 13"^ C. 



