LESSON 22.] FORMATION OF THE EMBRYO. 



139 



whole course of vegetation (12, &c.). So, in attempting to learn 

 how this growth took place, it will be best to adopt the same plan, 

 and to commence with the commencement, that is, with the first 

 formation of a plant. This may seem not so easy, because we have 

 to begin with parts too small to be seen without a good microscope, 

 and requiring much skill to dissect and exhibit. But it is by no 

 means difficult to describe them ; and with the aid of a few figured 

 we may hope to make the whole mat- 

 ter clear. 



383. The embryo in the ripe seed 

 is already a plant in miniature, as we 

 have learned in the Second, Third, 

 and Twenty-first Lessons. It is al- 

 ready provided with stem and leaves. 

 To learn how the plant began, there- 

 fore, we must go back to an earlier 

 period still ; namely, to the forma- 

 tion and 



384. Growth of the Embryo itself. 



For this purpose we return to the 

 ovule in the pistil of the flower (323). 

 During or soon after blossoming, a 

 cavity appears in the kernel or nu- 

 cleus of the ovule (Fig- 274, o), lined 

 with a delicate membrane, and so 

 forming a closed sac, named the 

 embryo-sac (s). In this sac or cav- 

 ity, at its upper end (viz. at the 

 end next the orifice of the ovule), 

 appears a roundish little vesicle or 

 bladder-like body (v), perhaps less 

 than one thousandth of an inch in 



diameter. This is the embryo, or rudimentary new plant, ai it* 

 very beginning. But this vesicle never becomes anything moie 

 than a grain of soft pulp, unless the ovule has been acted upor. by 

 the pollen. 



FIG. 328. Magnified pistil of Buckwheat ; the ovary and ovule divided lengthwise : roma 

 pollen on the stigmas, one grain distinctly showing its tube, which penetrates the stylr, re- 

 appears in the cavity of the ovary, enters the mouth of the ovule Co), and reaches the sur- 

 face of the embryo-sac (*\ near the embryonal vesicle (). 



