CH. I.] SOWING, 39 



Bui-ger found that rye seeds sown five inches and 

 a half deep, forced thek blades to the surface in 

 seventeen days and a half, but these remained green 

 only for six days and then \Nithered ; and that in 

 evei7 instance, the most shallow sown seeds pro- 

 duced the most stalks. I have observed the same in 

 the case of kidney beans, Windsor beans, and peas of 

 various vaiieties ; those seeds, buried one and a half 

 inch below the surface, invariably grew higher and 

 were more prolific than those buried at greater depths. 



From Saussure's experiments we leam that, weight 

 for weight, wheat and barley during germination 

 absorb less oxygen than peas, whilst these consume 

 less than beans and kidney beans. This explains 

 why, in proportion to their size, the two first may be 

 so^^•n at a greater depth below the soil's surface than 

 the three last named, without vegetation being pre- 

 vented. 



Seeds deposited at great depths, or similarly ex- 

 cluded from the air '\\ithin the Egyptian mummy 

 cerements, mil often retain their vegetative power 

 for an apparently unlimited time. Hence, earth 

 taken from far below the surface ■will often become 

 covered with charlock. This is an oleaginous-seeded 

 plant, and such, when thus excluded from the air, 

 retain their \itality most pertinaciously for reasons 

 already assigned. 



The atmosphere contains rather more than one- 



