16 



GROWTH OF THE PLANT FROM THE SEED. [LESSON 3. 



tercup or the Columbine, and in the Peony (Fig. 30, 31), where, 

 however, it is large enough to be distinguished by the naked eye. 

 Nothing is more curious than the various shapes and positions of 

 the embryo in the seed, nor more interesting than to watch its de- 

 velopment in germination. One point is still to be noticed, since 

 the botanist considers it of much importance, namely : 



32. The Kinds of Embryo as to the Number of Cotyledons, In all the 



figures, it is easy to see that the embryo, however various in shape, 

 is constructed on one and the same plan ; it consists of a radicle or 

 stemlet, with a pair of cotyledons on its summit. Botanists there- 

 fore call it dicotyledonous, an inconveniently long word to express 

 the fact that the embryo has two cotyledons or seed-leaves. In 

 many cases (as in the Buttercup), the cotyledons are indeed so 

 minute, that they are discerned only by the nick in the upper end 

 of the little embryo ; yet in germination they grow into a pair of 

 seed-leaves, just as in other cases where they are plain to be seen, 

 as leaves, in the seed. But in Indian Corn (Fig. 40), in Wheat, 

 the Onion, the Iris (Fig. 43), &c., it is well known that only one 



leaf appears at first from the 

 sprouting seed : in these the 

 embryo has only one cotyle- 

 don, and it is therefore termed 

 by the botanists monocotyledo- 

 nous ; an extremely long 

 word, like the other, of Greek derivation, which means one-cotyle- 

 doned. The rudiments of one or more other leaves are, indeed, 

 commonly present in this sort of embryo, as is plain to see in Indian 

 Corn (Fig. 38 - 40), but they form a bud situated above or within 

 the cotyledon, and enclosed by it more or less completely ; so that 

 they evidently belong to the plumule (16) ; and these leaves appear 

 in the seedling plantlet, each from within its predecessor, and there- 

 fore originating higher up on the forming stem (Fig. 42, 44). This 

 will readily be understood from the accompanying figures, with their 

 explanation, which the student may without difficulty verify for him- 



FIG. 38. A grain of Indian Corn, flatwise, cut away a little, so as to show the embryo, 

 lying on the albumen, which makes the principal bulk of the seed. 



FIG. 39. Another grain of Corn, cut through the middle in the opposite direction, divid- 

 ing the embryo through its thick cotyledon and its plumule, the latter consisting of two 

 leaves, one enclosing the other. 



FIG. 40. The embryo of Corn, taken out whole : the thick mass is the cotyledon ; the 

 navrow body partly enclosed by it is the plumule ; the little projection at its base is the very 

 short radicle enclosed in the sheathing base of the first leaf of the plumule. 



