X FILICINE.E LEPTOSFORANGIAT.-E 2>^7 



and the two resulting octants arc unequal in size. The follow- 

 ing divisions correspond for a short time in all the octants, but 

 soon show characteristic differences. For a short time each 

 octant shows a definite apical growth, the segments being cut 

 off by walls formed successively parallel to the three primary 

 divisions in the embryo, so that each octant may be said to 

 have a three-sided apical cell. When the octant wall in the 

 root quadrant is decidedly oblique this is not always evident in 

 the smaller octant, and the larger one in this case at once 

 becomes the definitive apical cell of the primary root. 



The first of these walls is usually parallel to the basal, the 

 second to the quadrant wall. Sometimes this order is reversed, 

 but never, apparently, is the first wall parallel with the octant 

 wall. Before the third segment is cut off from the octant, each 

 of the two first ones divides by a periclinal wall into an inner 

 and an outer cell. Each octant now consists of five cells, two 

 inner and three outer ones, of which one is the primary octant 

 cell, which still retains its original tetrahedral form. The 

 outer cell of each segment divides by a radial wall, but beyond 

 this the succession in the walls differs. Of the eight original 

 octants, one in each quadrant persists as the apical cell respectively 

 of cotyledon, stem, root, and foot, but in the latter it becomes 

 very early obliterated by the formation of a periclinal w^all and 

 further longitudinal divisions, which is the case also with one of 

 the octants in the leaf and root. In the stem both octants 

 persist, one becoming the permanent stem apex, the other 

 forming the apical cell of the second leaf. 



The Cotyledon 



Of the two primary octants of the cotyledon, one very early 

 ceases to grow and soon becomes indistinguishable, and the 

 subsequent growth is due almost entirely to the activity of a 

 single octant. The apical cell is at first like that of the other 

 members, tetrahedral, but after about two sets of segments 

 have been cut off from it no more are usually cut off from the 

 side of the apical cell parallel to the basal wall, and the three- 

 sided cell thus passes over into a two-sided one with segments 

 cut off alternately right and left. By the suppression of the 

 growth in the sister octant, the apical cell gradually assumes a 

 nearly median position. By the change to the two-sided form 



