LESSON 22.] FORMATION OF TIIU KMISKYO. 



139 



whole course of vegetation (12, Sec). So, in uttempting to leant 

 how this growth took place, it will be best lo 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 diiricult to describe them ; and with the aid of a few figures 

 we may hope to make the whole juat- 

 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. Growlli of the Embryo itself. 



For this purpose Ave 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 

 embri/o-sac (s). In this sac or cav- 

 ity, at its upper end (viz. at the 

 end next the orifice of tlic 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, at its 

 very beginning. But this vesicle never becomes anything more 

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

 the pollen. 



FFG. 328. Masinificl pistil of HurkwlM-at ; tl,r ovary and nvnir .Iivi,lo,I Irnstlnvise : some 

 pollen oil the stigmas, one (.-rain .listinrlly sl.ou ing its tulie, wlii.l. penetrates the stvie, re- 

 appears ill the cavity of tho ovary, enters tl.o month of the ovule (o), and reaches the sur- 

 face of the embryo-sac {s\ near the embryonal vesicle (u). 



