Germination of Forest Trees 57 



The data for the mesophilous species are given in Table XII. 

 The average figures at the bottom of the table show that germina- 

 tion began in dense shade, followed by medium shade and open 

 light ; that the germination period is longest in the case of the 

 dense shade ; that germination began first in the loam and last in 

 the gravel ; and that the germination period was shortest in loam. 

 Out of the 10 species listed in this table 7 germinated in the 

 dense shade before they did in the open light, 4 out of 8 species 

 showed longer germination period in the dense shade than in the 

 open light ; and 7 showed shorter germination periods in the loam 

 and sand than in the gravel. 



These three groups show exactly the same results so far as 

 light and soil moisture go. From the standpoint of soil texture 

 there are some interesting results. In the xerophilous species 

 germination usually begins in the gravel, in the xero-mesophilous 

 species it usually begins in the sand ; and in the mesophilous 

 species it usually begins in the loam, as the average figures and 

 number of species in each case testify. In the xerophilous 

 species the germination period is shortest in the loam and gravel, 

 in the xero-mesophilous it is shortest in the gravel, and in the 

 mesophilous species the period is shortest in the loam. That 

 xerophilous species germinate sooner in the sand and gravel than 

 in the loam is due undoubtedly to the amount of oxygen in these 

 soils. This suggests that oxygen is more necessary for the ger- 

 mination of xerophilous species than is the case in mesophilous 

 ones. In the mesophilous species germination begins sooner in 

 the loam indicating that soil moisture is more necessary to them 

 than oxygen. In the case of the light and the soil moisture 

 experiments it has been shown that favorable moisture conditions 

 lengthen the time of germination. In these cases it was found 

 that the shortest periods were in the open light and in the dry 

 soil. This same theory is proven in the case of the soil texture 

 experiments. It is well known that loam is favorable for ger- 

 mination on account of its moisture-retaining properties and that 

 gravel is favorable on account of its great amount of aeration. 

 Sand is intermediate between these and combines enough of the 

 soil moisture property of the loam with the aeration of the gravel 



