SEEDS AND SOWING. • 157 



results in a warm climate. It might be well to state 

 that the nature of the soil has also gieat influence on 

 the quantity of humidity at the disposal of the seed; 

 for example, when of a calcareous nature it will absorb 

 more than when sandy, and retain the same in greater 

 quantities when submitted to a higher temperature. 



Heat. — Evidently there exist certain limits w^hich 

 in either case should not be surpassed ; for example, if 

 the seed be placed in w^ater at a temperature of 122° 

 F. they will no longer germinate, as all the principles 

 of life will be destroyed. This temperature is never 

 attained after planting, and is consequently not to be 

 dreaded. The limits giving the best results are sup- 

 posed to be between 50° and 68° F. If the seeds 

 are in a good condition they will resist a very intense 

 cold, remaining ajiparently without life, and will make 

 their appearance above the surface soon after this cold 

 has ceased. If their germination has not commenced 

 the danger of destruction is not great, but, i"n the 

 contrary case, considerable losses are to be dreaded. 



Air. — It is impossible for seed to germinate without 

 this element, absorbing as they do large quantities of 

 oxj^gen, throwing off an equivalent of carbonic acid, 

 thus causing many internal changes, such as the trans- 

 formation of the albumen to gums, etc. There can be 

 no doubt as to the importance of a sufficient amount 

 of air, as experiments have been made to ascertain the 

 possibility of germination in presence of other given 

 gases, but were all without success, hence the import- 



