6 ? 
rishment is divided into two lobes called cotyledons ; 
the plume is the small white point between the 
upper part of the lobes ; and the radicle is the 
small curved cone at their base. * 
In wheat, and in many of the grasses, the organ 
of nourishment is a single part, and these plants 
are called monocotyledonous. In other cases it 
consists of more than two parts, when the plants 
are called polycotyledonous. In the greater number 
of instances, it is, however, simply divided into 
two, and is dicotyledonous . 
The matter of the seed, when examined in its 
common state, appears dead and inert : it exhibits 
neither the forms nor the functions of life. But 
let it be acted upon by moisture, heat, and air, and 
its organized powers are soon distinctly developed. 
The cotyledons expand, the membranes burst, the 
radicle acquires new matter, descends into the soil, 
and the plume rises towards the free air. By de- 
grees, the organs of nourishment of dicotyledonous 
plants become vascular, and are converted into 
seed leaves, and the perfect plant appears above 
the soil. Nature has provided the elements of 
germination on every part of the surface ; water 
and pure air and heat are universally active, and 
the means for the preservation and multiplication 
of life, are at once simple and grand. 
To enter into more minute details on the veget- 
able physiology would be incompatible with the 
objects of these Lectures. I have attempted only 
to give such general ideas on the subject, as may 
* Fig. 13. represents the garden bean; aa, the cotyledons, 
b, the plume, c , the radicle. 
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