100 
UPWARD GROWTH OF THE HEAD, AND [Part II. 
that is, besides the new growth towards the 
light, the parts of the stems which were already 
formed were bent towards the light. Three or 
four hours were sufficient to effect this change 
in these tender, drawn stems. 
Observing in the various experiments that 
several grass-seeds grew downward with their 
heads towards the light, and as plants with 
single-divisioned seeds grow with their heads 
single and not with the crane-neck, 1 imagined 
that they had not perhaps the same power of 
forcing themselves through the earth which 
plants, whose seeds have two divisions, have. 
I therefore 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 was first shown down¬ 
ward, 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 them¬ 
selves against the earth, the stems bowed down¬ 
ward, and sometimes bent short before the heads 
were disengaged. 
In the course of three weeks three plants of 
wheat forced their heads through about in. 
of earth, and showed themselves at the hole of 
