16 GROWTH OK TllF, I'LANT FROM THE SEED. [lESSON 3. 



tcrciip or the Colunibino, and in tho Peony (Fig. 30, 31), wliere, 

 however, it is large enough to he distinguished by the naked ey<?. 

 Nothing is more curious than the various shapes and positions of 

 the enihryo 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 ot'mucli importance, namely: — 



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



figures, it is easy to see that the embryo, however various in shaj)e. 

 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), Sec, it is well known that only one 

 /--~^ leaf appeai-s at first from the 



y^'^'^ ' ' '"'~''X ', /Tv sprouting seed: in these the 



] \ j /llll, t^'ifihryo has only one cotyle- 



^ ' I \ I v \\ m ^^"' ^"^ ^^ ^^ therefore termed 



V A.JIjL/ '/ K^^^J^ ^^i-J' ^y ^'"^ botanists monocotyJedo- 



38 39 40 nous ; — an extremely lung 



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 embr30, i\& 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 plumuh; (IC) ; 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 tlicir 

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



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

 lyinp on the allmnien, which makes tlic principal bulk of tho seed. 



FIG. 3'.>. Ant-llier prain of Corn, cut through tho middle in tlie opposite direction, divid- 

 ing tho cmt)ryo ihrcuch its tliick cotyledon and its plumule, the latter consisting of two 

 leaves, one enclosing the other. 



FIG. 40. The cml)ryo of Corn, taken out wliole : the tliick mass is the cotyledon ; the 

 narrow body partly enclosed by it is tho pluiiiiilo ; the Utile projection at its base is tlie very 

 short radicle CIltlJ■^•,•d in llie shouthiiig base of the fi»ot leaf of the plumule. 



