200 CALIFORNIA ACADEMY OF SCIENCES. 



the first, in each quadrant, may be looked upon as the 

 permanent apical cell of the organ derived from it. In 

 the cotyledon and stem, this does not always appear to be 

 the same one, but in the root it is always the larger of 

 the two octant cells. The next division is the same in 

 all the octants except the two smaller ones of the hypo- 

 basal half of the embryo, and consists of a curved wall 

 which divides them into two cells, which appear respect- 

 ively triangular and quadrilateral when seen from the 

 side. We may say that the triangular cell is the apical 

 one and the four-sided one its first segment (pi. iv, fig. 

 i6). 



THE COTYEEUON. 



In a cross-section of a ver}^ young embryo, the two 

 halves of the leaf quadrant appear exactly the same, and 

 it is impossible to say which of the two apical cells be- 

 comes the definite apical cell of the young leaf; but soon 

 one of these ceases to divide with any regularity and the 

 other grows more rapidly, divided by regularly arranged 

 segments, and functions, for a time at least, as the apical 

 cell of the young cotyledon (pi. iv, lig. i8, a, L''). How 

 long this continues was not further investigated, and not 

 infrequently the definite apical growth ceases at a very 

 early stage, as figured by Hanstein for J/, salvatrix, and 

 as frequently happens in Pilularia. 



THE STEM. 



The first divisions in the stem quadrant follow closely 

 those in the cotyledon, but here only one octant properly 

 goes to form the stem apex, and the other gives rise to 

 the second leaf, which grows at first in a manner entirely 

 similar to that of the stem, but about the time that the 

 cotyledon breaks through the prothalHum, begins to elon- 

 gate and soon becomes easilv distinguishable from the 

 stem. 



