16 



MOEPHOLOGY 



of an organ do not indicate its nature, either in the embryo or 

 in subsequent growth. But in all the cases yet mentioned the 

 cotyledons actually demonstrate their 

 nature by developing in germination 

 in a foliaceous manner and becoming 

 the first leaves of the seedling. Nor 

 is this nature much disguised by the 

 fact that the}' differ greatly in form in 

 different species, and that the seed- 

 leaves, or developed cotyledons, differ 

 much in shape and often in texture 

 from the succeeding leaves. (See Fig. 

 11, 12, 25, &c.) 



29. To complete the comparison 

 between the seedling Morning Glory 

 and that of the Maple, it is to be 

 noted that here, while the cotyledons 

 or seed-leaves are two, the following 

 internode bears only one leaf (Fig. 25), as also will the just de- 

 veloping third internode ; and this continues throughout up to 

 the blossom : that is, the leaves subsequent 

 to the cotyledons are not opposite as in the 

 Maple, but alternate. (13.) 



30. All the preceding illustrations are from 

 embryos which previous to germination have 

 developed nothing beyond the cotyledons. In 

 the following, a rudiment of further growth, 



26 2T 28 29 



or a primary terminal bud, is visible in the seed. It is most 

 manifest in large and strong embryos with thick or flesh}* cotyle- 



FIQ. 25. Further development of Morning Glory, Fig. 16, the root cut away, the 

 internode above the cotyledons and its leaf completed, the next internode and its leaf 

 appearing. 



FIG. 26. Embryo (kernel) of the Almond. 27. Same, with one cotyledon removed, 

 to show the plumule, a. 



FIG. 28. Section of an Apple-seed, magnified, cutting through the thickness of the 

 cotyledons. 29. Embryo of the same, extracted entire, the cotyledons a little separated, 



FIG. 30. Germination of the Cherry, showing the thick cotyledons little altered, 

 and the plumule developing the earliest real foliage. 



