18 



SEEDLINGS. 



[SECTION 3. 



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

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

 above. In its near relative, the Pea (Fig. 34, 35), this use of cotyledons 



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

 to the utmost, even into hemispheres ; the 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 hypogeeous. 



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 strong- 

 growing. Here, as seen in Fig. 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. 



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



Fio. 28. Embryo of Common Bean (Phaseolus 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, _ 



