THE ACORN AND ITS GERMINATION 19 



minate a fact which suggests that some profound mole- 

 cular or chemical changes have to be completed in the 

 living substance of the cells before further activity is 

 possible. We have other reasons for believing that 

 this is so, and that, until certain ferments have been 

 prepared in the cells, their protoplasm is unable to make 

 use of the food materials, and consequently unable to 

 initiate the changes necessary for growth. 



Sooner or later, however, and usually as the tempera- 

 ture rises in spring, the embryo in the acorn absorbs 

 water and oxygen, and swells, and the little radicle elon- 

 gates and drives its tip through the ruptured investments 

 at the thin end of the acorn, and at once turns downward, 

 and plunges slowly into the soil (fig. 3). This peculi- 

 arity of turning downwards is so marked that it manifests 

 itself no matter in what position the acorn lies, and it 

 is obviously of advantage to the plant that the radicle 

 should thus emerge first, and turn away from the light, 

 and grow as quickly as possible towards the centre of 

 the earth, because it thus establishes a first hold on the 

 soil, in readiness to absorb water and dissolve mineral 

 substances by the time the leaves open and require 

 them. 



The two cotyledons remain enclosed in the coats of 

 the acorn, and are not lifted up into the air ; the de- 

 veloping root obtains its food materials from the stores 

 in the cells of the cotyledons, as do all the parts of the 

 young seedling at this period. In fact, these stores in 

 the cotyledons contribute to the support of the baby 



c 2 



