THE WHEAT GRAIN AND PLANT 23 



period for which conclusive modern scientific experiments have 

 shown wheat to be viable is ten years. During six successive 

 years Saunders found the average viability of three varieties 

 to be respectively: 80, 82, 77, 37, 15 and 6 per cent. 1 Varro, 

 speaking of the granaries of the first century B. C., remarks 

 that the vitality of wheat can be preserved in them for 50 

 years. Daubeny questioned this in 1857, and stated that wheat 

 does not retain its vitality over 40 years. Humboldt states 

 that for causes not well known, Mexican grain is preserved with 

 difficulty for more than two or three years. The reported 

 germination of wheat taken from Egyptian mummies thou- 

 sands of years old is a modern myth originating in the im- 

 positions of fraud and cunning upon credulity. 



The highest temperature at which dry wheat seed can re- 

 tain its vitality is also an unsettled question. Chambers 's Cyclo- 

 pedia makes the statement that some dry seeds survive 212 F., 

 and 248 F., but does not state what kind. Klippart gives 

 58 F. as the point at which wheat loses its vitality, and says 

 that the germinating power is completely destroyed if the grain 

 is steeped 15 minutes in water having a temperature of 122 F. 

 According to the same writer, it could perhaps stand 170 F. 

 in a dry atmosphere without serious injury. He gives this as 

 a probable reason why wheat does not grow in the tropics, 

 where the soil often has a temperature of 190 F. Recent ex- 

 perience has shown that steeping wheat ten minutes in water 

 of 132 to 133 F. to kill smut germs does not injure its via- 

 bility. In northern Canada, 52 F. has no injurious effect 

 upon the vitality of dry and unplanted wheat. Beyond these 

 temperatures, no scientific experiments have been found recori- 

 ed by the author. 



Time Required for Ripening. The mean temperature required 

 for the successful cultivation and ripening of wheat has been 

 given as 65 F. for 45 to 60 days, and 55 F. for three or four 

 months of the growing season. Of the wheat in the United 

 States, according to the census of 1880, 67.5 per cent was 

 grown where the mean annual temperature was between 45 and 

 55 F., and 62.7 per cent of it where the annual rainfall was 

 between 35 and 50 inches. It has been claimed that the total 

 amount of sunshine and heat units required to mature a crop 

 1 Kept. Can. Exp. Farms, 1903, p. 44. 



