THE HIGHER CRYPTOGAMIA. 219 



lateral bands of the stem at right angles ; here the internal 

 septa of the annular wall become perpendicular, or even 

 overhanging. Its cells appear arranged in concentrical 

 scaly layers round the middle point of the stem-bud. 



During the formation of the annular wall the activity of 

 cell-multiplication in the longitudinal direction (i. e., in the 

 direction of lines drawn in a radiating manner from the 

 apex of the stem-bud along its sides) increases, and 

 obliterates the arrangement of the cells visible in the apical 

 aspect of the youngest portions of the bud, viz., the system 

 of flattened arcs surrounding the middle point of the stem. 

 In its place the arrangement in (apparently radial) longitu- 

 dinal rows becomes more manifest ; this is produced by the 

 repeated division of the cells by means of septa at right 

 angles to the outer surface, and perpendicular to the radial 

 planes passing through the axis of the stem. 



The prolongation of the two primary axile vascular bun- 

 dles begins to be differentiated from the rest of the tissue 

 at a very little distance beneath the terminal bud, and in 

 or near the mass of cells derived from the eighth-youngest 

 cell of the second degree. The separation of the peripheral 

 vascular bundle commences somewhat further from the 

 apex of the stem. Both phenomena arise from the fact, 

 that in the strings of cells which are transformed into 

 vascular bundles, the transverse division which continues 

 to take place in the neighbouring tissue, diminishes and 

 ceases, whilst the division by means of longitudinal septa is 

 hastened. The rudimentary vascular bundles appear there- 

 fore as streaks of narrow elongated cells, whilst in the cells 

 of the remaining tissue no one of the three dimensions 

 preponderates to any great extent (PI. XXXI, figs. 4, 5). 

 Certain cells of the vascular bundles arranged in longitu- 

 dinal rows, become widened at a very early period. After- 

 wards they are transformed into the scalariform cells which 

 form the principal mass of the perfect vascular bundle. 

 In the first instance they are placed one upon another, and 

 furnished with horizontal transverse septa : they assume 

 their permanent spindle shape even before the first traces 

 of thickening layers are visible upon their inner walls (PI. 

 XXX, fig. 12 ; PI. XXXI, fig. 1). The first appearance 



