SECTION 3.] 



SEEDLINGS. 



19 



28. This hypogaom germination is exemplified on a larger scale by the 

 Oak (Fig. 36, 37) and Horse-chestnut (Fig. 38, 39); but in these the 

 downward growth is wholly a stout tap-root. It is not the caulicle ; for 



this lengthens hardly any. Indeed, the earliest growth which carries 

 the very short caulicle out of the shell comes from the formation of foot- 

 stalks to the cotyledons ; above these develops the strong plumule, below 

 grows the stout root. The growth is at first entirely, for a long time 



FIG. 31. A Beech-nut, cut across. 32. Beginning germination of the Beech, 

 showing the plumule growing before the cotyledons have opened or the root has 

 scarcely formed. 33. The same, a little later, with the plumule-leaves developing, 

 and elevated on a long internode. 



FIG. 34. Embryo of Pea, i. e. a pea with the coats removed; the short and 

 thick caulicle presented to view. 35. Same in advanced germination : the plumuia 

 eas developed four or five internodes, bearing single leaves ; but the first and sec. 

 ond leaves are mere scales, the third begins to serve as foliage ; the next more so. 



