150 



FERTIUZATION. 



first expands into a proper cell, and is usually attached 

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

 vides itself transversely, becoming two cells; the upper 

 tlongates either with or without subdivisionj 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. Schlbiden's view. Owing to the ex- 

 treme difficulty of observation in this minute 

 field, different views of this process have been 

 advanced. That of Schleiden 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 



, Growth of the emlryo ., , 



In HippMis vulgaris. Thoferti- the embryo sac. 



feed cell has divided itselt in- ^gg FeETILIZATION IN THE CONIFERS, 



to several, of which c, 6, con- 

 stitute the euspensor attached Where no style or stigma exists, as in the Coni- 

 to theapejtofthesae; a, eni- f ^j^^ jj^jj fg^jjg directly into the micropyle 

 bryo dividing into 2, then into ' ^ . . , ^ • ^ 



4 cells. of the naked ovule and its tubes settle mto the 



tissue of the nucleus. 



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 occur in 

 the seed at the recommencement of ... -. ,„,,.,, . . 



. , . 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 "'"'' f Sohieiden. p, Poiien; t, 



. , !,• 1 tuhe, r, raphe ; c, chnlaza; b, pi-iminej 



solution which shall contain the proper «, secundine ; n, nucleus ; «, sac which 



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

 tliat 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. 



