CH. HI. 



DOWNWARD GROWTH OF THE ROOTS. 



91 



Observing in the various experiments that several 

 grass-seeds grew downward with their heads towards 

 the hght, and as plants with single-divisioned seeds 

 grow with their heads single and not with the crane- 

 neck, I imagined that they had not perhaps the same 

 power of forcing themselves through the earth which 

 plants whose seeds have two divisions have. I there- 

 fore tried wheat, barley, and oats, which, as well as 

 the grasses, are monocotyledonous ; that is, have a 

 single or undivided seed. A great quantity of root 

 w^as first shown downward, and ceased to grow. The 

 heads then came down and grew towards the light. 

 The roots fixed themselves upward and the plants 

 grew. When the heads of any engaged themselves 

 against the earth, tlie stems bowed downward, and 

 sometimes bent short before the heads were dis- 

 engaged. 



In the course of three weeks three plants of wheat 

 forced their heads through about 7| inches of earth, 

 and showed themselves at the hole of the flower-pot. 

 They, however, ceased to grow, being possibly beaten 

 down by the watering. 



Probably one reason which enables these delicate Provision 



to enable 



organisations to dispense with the crane-neck in thegem- 



mule of a 



thrusting themselves through the hard earth is, that ^^^1^^' 

 they are entirely single-leadered, instead of having thrSSt^tsei 

 leaflets branching sideways hke the gemmules of tiirea^rtb. 

 double-seeded plantules. But, beside this, the single 

 tender blade is rolled round on itself, and enveloped in 



