SEEDS AND SOWING. 163 



In France the average mean' of 6° C. (42.8° F.), 

 made at a depth of 6 to 8 cm. (2.3 to 3.1 inches) is con- 

 sidered to be an excellent guide, when this for several 

 days in succession is constant. 



When the seed is placed in the soil under favoring 

 circumstances the germination commences, the outer 

 surface swells, and, during this period, has a most ex- 

 traordinary force. The embryo feeding itself on the 

 albumen for a certain time, the radicle then shows 

 itself by a small white point ; this penetrates the soil 

 more and more. The other extremity is where the 

 future cotyledons appear after several days. These 

 still have their ends in the interior of the embryo. 

 This doubled portion then gains the upper surface of 

 the soil, where in contact with the light and exterior 

 heat it soon expands, and the two small green leaves 

 become visible ; radicles seem to adhere to the outer sur- 

 face of the root, these greatly facilitating the extraction 

 of the nourishment from the surrounding soil, and are 

 assisted by the above. The portion situated between 

 the leaves and the extremity of the plant below the 

 surface actually represents the final root. It can now 



' What we wish to convey by " averi^e mean" is that observations are taken 

 morning, afternoon, and evening. For example : — 



Supposing 6 o'clock in the morning the temperature 36° Fahr. 

 " 12 " " afternoon " 48° " 



" 6 " " evening " 42° " 



1260 " 



126 

 The average mean for the day would be -^ = 42° F. 



