OF THE EMBRYO AND SEEDLING. 



19 



32. Thus, in the Pea, near relative of the Bean, the embryo 

 (Fig. 37), which is the whole kernel of the seed, has the 

 cotyledons so gorged with this nutritive 

 store that they are hemispherical ; and 

 the acorn of the Oak (Fig. 39), near 

 relative of the Beech, is in similar case. 

 These extremely obese cotyledons have 

 not only lost all likeness to leaves, but all 

 power of fulfilling the office of foliage, 

 which is apparently no disadvantage ; for 

 when two different duties are performed 

 by the same organ, it rarely performs both 

 equally well. Here they become mere 

 receptacles of prepared food, the nature 

 and office of which is the same as of the 

 albumen, or nutritive deposit exterior to 

 the embryo in what are called albuminous 

 seeds. (25-27.) The difference is in the 

 place rather than in the character of the 

 deposit. The plumule in such cases is 

 always apparent before germination ; and 

 it develops even with more vigor than in 

 the preceding cases. It usually rises as a 

 stout stem of several internodes lengthen- 

 ing almost simultaneously, or at least the 

 upper strongly developing long before the 

 lower have finished their growth ; and 

 the latter are practically leafless, bearing 

 only small and scale-like and useless ru- 

 diments of leaves. This is correlated with 

 the peculiarity that the caulicle does not 

 lengthen in germination, or it lengthens 

 very slightly ; the cotyledons remain within 

 the coats of the seed ; and if this were 

 buried beneath the surface of the ground, there it remains. The 

 abortion of the earliest leaves of the plumule is in correlation 

 with this hypogceous (i. e. underground) situation of the cotyle- 

 dons throughout the germination. The slight elongation of the 

 caulicle serves merely to protrude its root-end from the coats of 

 the seed in a downward direction, and from this a strong root 

 usually is formed. 



FIG. 39. Section of an acorn, filled by the embryo. 40. Advanced germination 01 

 the same. 



