160 



FERTILIZATION. 



first expands infx) a proper cell, and is usually attached 

 to the wall of the sac near the micropyle. It then di- 

 vides itself transversely, becoming two cells ; the upper 

 elongates either with or without subdivision, forming a 

 filament (suspensor) ; the lower cell enlarges by subdi- 

 vision, first spherically, and afterwards the little mass 

 begins to take form according to the species, showing 

 cotyledons, plumule, etc., until fully developed into the 

 embryo. 



759. Schleiden's vie"w. Owing to the ex- 

 treme difficulty of observation in this minute 

 field, different views of this process have been 

 advanced. That of Sohleiden should not be 

 overlooked. He maintains that the end of the 

 pollen tube actually penetrates the sac and itself 

 becomes the embryonic cell. The pollen grain is 

 in this view the primitive cell, and is itself 

 quickened into development by the contents of 



608, Growth of the eml ryo .i v 



in Hippuris vulgaris. The ferti- the embryo sac. 



tized cell has divided itsellin- ^ FERTILIZATION IN THE CONIFERS 

 to several, of which c, &, con- 

 stitute the sw^mso)- attached WJicre no style or stigma exists, as in the Coni- 

 totheapexofthesac; a,em-j;.,,. ^.j,^, „g,^ fjj|,^ directly into the micTopyle 



Dryo dividing iQto 2, then into J- , . i • i 



of the naked ovule and its tubes settle mto the 

 'tissue of the nucleus. 



i cells. 



761. Chemical' changes in germina- 

 tion. The ovule matures with the com- 

 pletion of the embryo, and passes into 

 the fixed state of the seed in which the 

 embryo sleeps. A store of nutritive 

 matter, starch, gluten, etc., is thought- 

 fully provided in the seed for the use of 

 the young plant in germination, until its 

 root has gained fast hold of the soil. 



762. The changes which occdr in 

 THE SEED at the recommencement of -„„ n i <■ tt- i * ■ , 



609, Ovule of Viola tricolor, showing 



growth, are simply such as are requisite the process of fertilization according to 

 to reduce its dry, insoluble deposits to a f^ ^'''^" f Schieiden. p Poiien ; u 



-'' ^ ^ tube, r, raphe ; c, chalaza; &, pnmine ; 



solution which shall contain the proper a, secundine ; n, nucleus ; .s, sac which 



materials for cell-formation or growth ; t''" 'i^'^e appears to have penetrated. 

 that is, gluten and other nitrogenous matters, oil, starch, etc., are to be 

 changed to diastase, the same as yeast, and dextrine, the same as gum 

 or grape sugar. 



