The Seed in Plant Production 389 



consequently a large bulk of material which must be cured 

 previous to threshing. 



In harvesting and storing seed the unfortunate practice 

 often prevails of storing the product in bulk; this in spite 

 of the fact that no small proportion may be somewhat 

 immature. As a common result, the material heats rapidly, 

 and in the end much loss may occur (see section 168). 

 This heating is due in many cases to respiration, yet a part 

 of the difficulty also lies in the fact that the growth of 

 microorganisms is much encouraged by the "sweating 

 process." 



230. Duration of vitality. In recent years considerable 

 attention has been bestowed upon the problems of main- 

 tenance of seed vitality, and upon a determination of the 

 conditions which are injurious. Much new work and 

 valuable data are therefore available; but the problem 

 is not a new one, and much was done by De Candolle and 

 others fully eighty years ago. 



Species differ in a decided manner with respect to the 

 length of time in which vitality is maintained, and this is 

 true whether the conditions to which they are subjected 

 are favorable or unfavorable. Among seeds readily killed 

 by storage for a relatively short period may be included 

 those of many Compositse, Cruciferae, and Gramineae; 

 while some of those far more resistant are Malvaceae, 

 Solanaceae, hard-seeded Leguminosae, and in general those 

 with water or air-resistant seed-coats. It should not be 

 understood, however, that all species of the same genus 

 or family are even approximately alike in resistance. 

 Becquerel reports an age of about eighty years for several 

 species of legumes which were still capable of germination. 



