VITALITY OF DRY SEEDS 419 



There is, through prolonged periods, no appreciable dimi- 

 nution in the food stores, no growth, and no deterioration 

 of the protoplasm. When vitality is finally lost the cause 

 may be, as Crocker (1916) believes, a slow and cumulative 

 coagulation of the proteins of the living matter. White 

 has shown that wheat seeds still contain active enzymes 

 when 20 years old — that is, many years after losing the 

 power of germination. 



Seeds in Dry Air. — The seeds of some species of Oxalis 

 germinate as soon as they leave the capsule and die quickly 

 if exposed to dry air. The seeds of the willows retain their 

 power of germination for a few days only. The seeds of the 

 cocoa, the coconut, the para rubber are also short-lived, 

 making their transport difficult. The overwhelming majority 

 of seeds, however, can lie dormant for a few months, at least 

 till the growing season following their formation. In some, 

 e.g. the beech, the percentage of germination falls greatly 

 by the second year, but many, perhaps most, can rest for 

 longer. The power of germination of the wheat is lost, 

 according to White (1909), only after from 11 to 16 years, 

 of the barley after 8 to 10, of the oats after 5 to 9, and of the 

 maize and rye after 5 years. The possibility of still longer 

 periods of potential rest is difficult to control. Many 

 exaggerated statements have been made, as that the mummy 

 wheat from Egyptian tombs is still capable of germination, 

 which is certainly not true. Exact investigations on her- 

 barium and stored seed of known age have been made by 

 Ewart (1908) and Becquerel (1907), and a review of the 

 subject has been wiitten by F. F. Blackman (1909). 

 Becquerel tested the germinating capacity of seeds of known 

 age up to 135 years in the herbarium of the Natural History 

 Museum of Paris. He found 7 species, 4 Leguminos^, 

 and I each Malvaceae, Labiatas, and Nelumbiaceas, which 

 retained their power of germination after 50 years, the 

 extreme case being Cassia hicapsularis which germinated 

 after 87 years. Of 500 species tested 50 possessed seeds 

 which germinated after 25 years. Of the seeds which had 

 lain in the herbarium from the reign of Louis XVI none 



