18 



SEEDLINGS. 



[SECTION 3. 



upon the surface of the soil, the flat but thick cotyledons remaining in it, 

 and supplying food for the growth of the root below and the plumule 

 tbove> In its near relative, the Pea (fig. 34, 35), this use of cotyledons 



for storage only is most completely carried out. For they are thickened 

 to the utmost, even into hemispheres ; tlie caulicle does not lengthen at all ; 

 merely sends out roots from the lower end, and develops its strong plu- 

 mule from the upper, the seed remaining unmoved underground. That is, 

 in technical language, the germination is hypogmons. 



27. There is sufficient nourishment in the cotyledons of a pea to make 

 a very considerable growth before any actual foliage is required. So it 

 is the stem-portion of the plumule which is at first conspicuous and strcug- 

 growing. Here, as seen in Pig. 35, its lower nodes bear each a useless 

 leaf-scale instead of an efficient leaf, and only the later ones bear leaves 

 fitted for foliage. 



PiQ. 26. Embryo of Pumpkin-seed, partly opened. 27. Young seedling of same. 



FiQ. 28. Embryo of Common Bean ( Pliaseolus vulgaris) : caulicle bent down 

 over edge of cotyledons. 29. Same germinating : caulicle well lengthened and root 

 beginning; thick cotyledons partly spreading; and plumule (pair of leaves) growing 

 between them. 30. Same, older, with plumule developed into internode and 

 pair of leaves. 



