132 HOFMEISTER, ON 



In slender branches, especially those which hang down- 

 wards, the bark consists very regularly of only eight longi- 

 tudinal rows of cells. In the younger parts of the bud 

 the axile cells of the stem are more elongated longitudinally 

 than the peripheral cells, a circumstance which has a 

 remarkable influence upon the slender form of the end of 

 the stem. The arrangement of the cells of the interior of 

 the stem into triangular plates, inclined inwards to the 

 axis of the stem, arises from the fact that all the cells of 

 the third part of a transverse section of the stem are 

 derived from a single cell of the third degree. Each of 

 these plates is higher by a portion of the length of a cell 

 than the adjoining plate on one side of it, and is exceeded 

 by the same portion of the length of a cell by the similar 

 plate on the other side of it. The difference of height of 

 two such cellular plates is almost always less than half a 

 cell, a circumstance from which it must be concluded that 

 the elongation of the cells of the stem preponderates in 

 their upper portions. The above-mentioned arrangement 

 is most clearly seen in a perfectly axile longitudinal section 

 of a Sphagnum bud, made at some distance from the apex ; 

 if the section deviates only slightly from the longitudinal 

 axis of the bud, the arrangement is partially or entirely 

 indistinguishable. 



In all the cells of the periphery of the stem (with the 

 exception of the cells of insertion of the leaves) a transverse 

 division occurs a short time before, or contemporaneously 

 with, the termination of the cell-multiplication of the end 

 of the stem, in a radial direction (PL XVII, figs. 1, 7). 

 This multiplication does not continue in the cells of the 

 interior of the stem, which are elongated, instead, during 

 its continuance, to about double their former length ; by 

 this means the short-celled bark is differentiated from the 

 long-celled axile-tissue. The multiplication of the stem- 

 cells in the diametral direction is caused by the division 

 of the slightly elongated cells of the interior of the 

 stem, by means of septa tangential to the axis of the stem, 

 alternating with divisions by radial longitudinal septa. 

 The number of these cells in the transverse diameter of 

 the stem increases tenfold from the place of insertion of 



