March, 1913. 



KNOWLEDGE. 



87 



The seeds under dis- 

 cussion were kept in 

 paper bags in a drawer 

 of the laboratory, and, 

 therefore, may be pre- 

 sumed to have been 

 subjected to fairly con- 

 stantconditionsof mois- 

 ture and temperature. 



Oats kept under 

 similar conditions 

 maintained their vital- 

 ity for from five to seven 

 years longer and, taken 

 in conjunction with 

 previous observations, 

 may be said to supply 

 the key to the results 

 of the long list of 

 experiments made by 



Carruthers. " The difference between wheat and 

 barley on the one hand, and oats on the other, is the 

 greater protection afforded to the embryo of the oats 

 by the fact that in its case the glumes, which fall 

 off as chaff in the wheat and barley, remain attached 

 to the seed." 



The cause which decides whether germination or 

 death shall result in the embryo of a seed is the 

 balance between heat and moisture. 



Heat is, perhaps, the greater factor, if it is possible 

 to speak so of two essentials, in deciding germination, 

 whilst moisture may be said to govern vitality. 



By this is meant that whilst moisture without 

 heat, or heat without moisture, is incapable of produc- 



Figure 86. 

 Rivet Wheat, longitudinal section. 



Figure 87. 

 Rivet Wheat, transverse section. 



about 1 J0°F without life becoming extinct. 



It would perhaps be more correct to say that in 

 the case of germination, the balance between heat 

 and moisture is finer than when the death of the 

 embrvo within the seed alone has to be considered, 

 when, though the loss of moisture beyond a certain 

 point means death, the temperature to which the 

 seed is subjected may be varied within very wide 

 limits without appreciable loss of vitality. 



In the case of genuine Mummy Wheat, that is 

 wheat found in the tombs of Egyptian mummies of 

 known antiquity, heat existed without the necessary 

 moisture to bring about germination, and the gradual 

 desiccation of the berries reduced the moisture con- 



ing germination, yet the heat optimum applied to a tent of the embryo below that with which life within 

 seed with a minimum of moisture, is more likely to the seed remained possible. 



produce germination than a maximum of moisture The same cause brought about the death of the 



present with a minimum of heat. In the other case, seeds examined by Carruthers, who states that it 

 moisture must be present in the embryo plant if life was no " chemical alteration produced by tern- 

 is to be retained, though air-dried seeds have been perature, but the steadv loss of moisture going on 

 exposed for some days to a temperature very far continually at ordinary air temperature." 

 below freezing point, or, again, to an upper limit of After life is extinct the changes which take 



place within the wheat 

 grain are more chem- 

 ical than bacteriological 

 in the case of Mummy 

 Wheat at any rate, for 

 the presence of such 

 powerful antiseptics as 

 bitumen and essential 

 oils (both of which are 

 very apparent in the 

 smell of the Egyptian 

 Mummy Wheat here 

 examined) is sufficient 

 to prevent the action 

 of moulds or bacteria. 



The exact nature of 



these changes will be 



discussed more fully in 



Figure 85. a later section. 



Wheat of the year 1854, transverse section. The Mummy Wheat 



Figure 84. 

 Wheat of the year 1854, longitudinal section. 



