700 



the dii'loid j-hase has coaie to occupy tlie greater i.ortion of 

 the life history. 



The tiological meaning of tlas appareiitlj' ^^eneral tend- 

 ency in the evoli;tion of pls,nt structures is hinted at "by 

 the experiments of GPIRASSIl'.O^, ('01). Aftei- studying the 

 growth of vegetative cells of Spii''0":rra in y/hich nuclei 

 had Ijeen induced to fuse, GERAoF;IMOW,cJ'.' -e to tlie conclusion 

 t}iat the grov/th of a cell which has an u.nusual amount of 

 nuclear material is more vigorous than that of a cell with 

 the USU9.1 nuclear content. The cell wall, the chrojiiato- 

 phores, and apparently the protopla.sin grow more vigorously. 

 Such cells divide only after they have reached a size nc- 

 ticeahly larger than norme,l. (see Bot. Ga^, . 3_5, 224-5, 

 »03). 



If, then, the presence of nuclei v/itli the douole 

 chrome tin content impcirts greater vigor to the cell, we 

 should e:-;pect to find some evidence of this greater vigor 

 not only in the size, hut in the rate of growtli of the tet- 

 rasporic plants of Griff ithsia . A comparison of sexual 

 plants with tetraspoi-ic plants does not reveal any constant 

 difference in the size of the resting nuclei or in the size 

 of the cells of the two ki^ds of individuals. However, a 

 comparison of those cells of tlie diploid individual which 



