218 HOFMEISTEll, ON 



cone. These divide successively by means of longitudinal 

 septa which are parallel to each one of their small lateral sur- 

 faces, and diverge strongly from the radii of the stem, into 

 from three to five cells, adjoining the cell of the first 

 degree (PI. XXXI, fig. 3 5 ) ; a form of multiplication in 

 which variations sometimes occur by which the next step 

 in the development is anticipated (PL XXXI, fig. 2). The 

 newly-formed cells then divide gradually by means of septa 

 parallel to the lateral surface of the apical cell into twos ; 

 those cells which are situated anteriorly to the middle of 

 the sides of the apical cell dividing sooner than those 

 adjoining the lateral comers. The cells thus formed, whose 

 increase in height and in width (i. e., parallel to the lateral 

 surface of the apical cell) far exceeds their increase in thick- 

 ness, divide by means of transverse septa into low, almost 

 cubical, inner cells, and elongated outer cells, with a free 

 outer wall (PI. XXXI, figs. 4, 5). The expansion and 

 multiplication of the cells of each of the groups derived 

 from a cell of the second degree, preponderate considerably 

 in the lower portion and in a transverse direction ; and 

 the same thing occurs in the cells derived from the youngest 

 of the four cells of the second degree, whose free outer 

 walls compose the conical interior portion of the stem-bud 

 (PL XXXI, figs. 4, 5). In the longitudinal section of the 

 stem the boundary lines which enclose each such group of 

 cells exhibit strongly protruding angles on the side turned 

 away from the apex of the stem : the side walls of the cells 

 composing the outer surface of the stem-bud, are inclined 

 inwards towards their summits. In the next older group 

 of cells the direction of the suddenly-augmented cell-multi- 

 plication is reversed. Here the cells of the circumference 

 often divide repeatedly by means of septa parallel to the 

 chord of the arc of the outer wall, and perpendicular to the 

 side-walls. This is a growth in thickness, an increase of 

 the cortical tissue in a direction at right angles to the 

 axis, but in consequence of the unusual direction of the 

 cells in which it occurs, it takes place at first apparently 

 in an upward direction. The bud becomes surrounded by 

 a high, narrow, annular wall. The growth of the latter is 

 particularly active in the direction of a plane cutting the 



