1917] GROVES— DURATION OF SEEDS 1S5 



seeds, such as Drosera, willow, and poplar. A series of determina- 

 tions should also be made on seeds at constant temperature with 

 variations in moisture content to ascertain the relations existing 

 between moisture content and life duration. 



The data show that the Lepeschkin formula applies as a 

 temperature-life duration formula for seeds at the temperatures 

 used in these experiments, but there are several considerations 

 that may limit its application at lower temperatures, including 

 ordinary storage temperatures. (1) Increase of acidity of seeds 

 will hasten the coagulation of the cell proteins; such a change is 

 known to occur in the seeds of certain Rosaceae (15a), at least if 

 stored in the imbibed condition. (2) Lepeschkin (22) found that 

 in active plant cells a redispersal of cell proteins is going on coin- 

 cidentally with coagulation. As a consequence, at high tempera- 

 tures where the coagulation was rapid, the found and calculated 

 life durations agree closely; while at lower temperatures, where 

 redispersal is prominent, the calculated life durations are much 

 shorter than the found values. In seeds the calculated values are 

 usually much greater than records of longevity at room tempera- 

 tures. This indicates that the redispersal process is not going 

 on in relatively dry seeds, or, if it is, it is more than counteracted 

 by some other process. (3) A slight error in the value of the 

 constant b in formula 3 will give a relatively large absolute error 

 for a life duration at low temperatures such as o° C. At higher 

 temperatures the absolute error becomes less. (4) The lower 

 the water content of seeds, the more heating they withstand and 

 the greater the longevity at moderate and lower temperatures. 

 This law has its limits, for excessive drying is itself injurious. In 

 seeds that will endure desiccation, injury sets in with a reduction 

 of the water content considerably below 2 per cent, while in forms 

 like Drosera it appears before air-dry condition is reached. The 

 formula, of course, is limited to degrees of desiccation less marked 

 than those producing injury. (5) It is possible that slow oxidation 

 may limit the longevity of seeds. If this be true, hard seeds with 

 their coats impervious to gases along with their constant low per- 

 centage of water are in an especially favorable condition for the 



