14 



GROWTH OK THE PLANT FROM THE SEED. [LESSON 3- 



earliest growth. On cutting open the seed, however, we find this 



embryo (considerably crumpled or folded together, so as to occupy 



less space, Fig. 25) to be surround- 

 ed by a mass of rich, mucilaginous 

 matter (becoming rather hard and 

 solid when dry), which forms the 

 principal bulk of the seed. Upon 

 this stock the embryo feeds in ger- 

 mination ; the seed-leaves absorbing 

 it into their tissue as it is rendered 

 soluble (through certain chemical 

 changes) and dissolved by the wa- 

 ter which the germinating seed im- 

 bibes from the moist soil. Having 

 by this aid 25 ss 



lengthened 

 its radicle 

 into a stem 

 of consider- 

 able length, 



and formed the beginning of a root at its 



lower end, already imbedded in the soil 



(Fig. 27), the cotyledons now disengage 



themselves from the seed-coats, and ex- 

 pand in the light as the first pair of leaves 



(Fig. 28). These immediately begin to 



elaborate, under the sun's influence, what 



the root imbibes from the soil, and the new 



nourishment so produced is used, partly to 



increase the size of the little stem, root, 



and leaves already existing, and partly to 



produce a second joint of stem with its 



leaf (Fig. 29), then a third with its leaf 



(Fig. 8) ; arid so on. 



31. This maternal store of food, deposited in the seed along with 



the embryo (but not in its substance), the old botanists likened to 



FIG. 23. Buckeye : a seed divided. 24. A similar seed in nomination. 



FIG. 2f. Sood and emhryo of Morning-Glory, cut across, t?-. Kmhryo of the same, de- 

 tached and straightened. 27. Germinating Morning-Glory. 28. The same further advanced; 

 us two thm seed-leaves expanded. 



