section I oo^ol-iior v/iui uJie U/o ceils al'tonya/d cut. oil" 

 from the primary periblom of thic section, divide re.p ■ . 

 "by mtin;- periclines ai'id longitudinal anticlines (Fi^-^s. 4, 

 12 - ir). Later transverse anticlines appear, the first 

 one beinf; in about the tenth segnien' from the apical cell 

 of a leaf of the size shovm in Fig, 1-. In section II a 

 longitudinal anticline is fomied in the pleromo coll par- 

 alell to the median v/all; then a similar v/all erpindicular 

 to this divides tlie plerome into quiirters (Figs. 13 - 1~). 

 Of these, the cell in tlie angle between sections I -Jid 

 III (tr.,Figs. 5, 10 - 19) never divides further, but be- 

 comes directly the large trachea of its side of th.e sjcial 

 bundle. Tliough no division walls are formed in this its 

 nucleus divides actively, so ■'"hat in a trachea of lialf a 

 millimeter in length (Fig. G), there may be twen'y-five or 

 thirty nucleipresent. Later Uiese and the otlier protoplas- 

 mic contents of the trachea disappear, v/hile the end walls, 

 which are portions of the original se.gment walls, assume 

 gradually the oblique position characteris ic of these in 

 the mature trachea (Fig. C). Tlieir inclination is always 

 dovmwards and dorsal as shovm in the figiu'e. Th.is is tlie 

 only cell of the segment tliat remains of the full length 

 of a segment for any considerable time during the devel- 

 opment. 



Tlie other three qiiarters of Mils section, and all the 



