6EBMINATION. 355 



exhausted, and the young plant is wholly cast upon its 

 own resources. 



At 41 F., in the experiments of Haberlandt, the root- 

 let issued after four days, in the case of rye, and in five 

 to seven days in that of the other grains and clover. 

 The sugar-beet, however, lay at this temperature 22 days 

 before beginning to sprout. 



At 51, the time was shortened about one-half in case 

 of the seeds just mentioned. Maize required 11, kidney- 

 beans 8, and tobacco 31 days at this temperature. 



At 65 the cereals, clover, peas, and flax began to 

 sprout in one to two days ; maize, beans, and sugar-beet 

 in three days, and tobacco in six days. 



The time of completion varies with the temperature 

 much more than that of beginning. It is, for example, 

 according to Sachs, 



at 4155 for wheat and barley 4045 days, 

 at 95 100 " " 10-12 



At a given temperature small seeds complete germina- 

 tion much sooner than large ones. Thus at 55-60 the 

 process is finished 



with beans in 3040 days. 

 " maize in 30-35 " 

 " wheat in 2*-25 

 " clover in 810 " 



These differences are simply due to the fact that the 

 smaller seeds have smaller stores of nutriment for the 

 young plant, and are therefore more quickly exhausted. 



Proper Depth of Sowing. The soil is usually the 

 medium of moisture, warmth, etc., to the seed, and it 

 affects germination only as it influences the supply of 

 these agencies ; it is not otherwise essential to the pro- 

 cess. The burying of seeds, when sown in the field or 

 garden, serves to cover them away from birds and keep 

 them from drying up. In the forest, at spring-time, we 

 may see innumerable seeds sprouting upon the surface, 

 or but half covered with decayed leaves. 



