314 H0FMEISTE11, ON 



sists, in its lower portion, of the hinder side of its own par- 

 ticular stipule, and in its upper portion, of the stipule of 

 the next older frond. The greater part of the wall which 

 is turned towards the hinder side of the frond, is composed 

 of the front surface of the stipule of the third youngest 

 frond, and the remainder of the latter wall is formed of 

 the front surface of the stipule of the second youngest frond. 

 The different stipules amalgamate at all points of contact 

 with the exception of those points which are coincident 

 with a line perpendicular to the apical cell of the stem. 

 Consequently there remains a very narrow open canal 

 leading to the apex of the stem into which the different 

 cavities enclosing the fronds debouch by a small opening 

 (PL XLI, figs. 1, 2). 



If a careful section be made through that part of the 

 stem in which the punctum vegetationis lies, the three- 

 sided apical cell of the stem is seen at the base of the 

 canal* leading to the punctum vegetationis, surrounded by 

 the youngest secondary cells (PI. XLI, fig. 4). Longitu- 

 dinal sections through the terminal bud (PI. XLI, fig. 2 J ). 

 exhibit most distinctly the deep depression of the apex of 

 the stem into the prematurely developed peripheral tissue ; 

 a phenomenon which, here as elsewhere, depends upon an 

 early • vigorous diametral cell-multiplication accompanied 

 by a very slight almost obsolete longitudinal cell-multipli- 

 cation. 



The course of the vascular bundles of OjjMo^lossum is 

 simple ; they form a cylindrical net, one of the meshes of 

 which corresponds with each frond, and sends out to the 

 frond a vascular bundle from its apical angle. Frequently, 

 however, all the cellular tissue which fills up the 

 meshes is transformed into scalariform vessels, so that the 

 stem then, for considerable distances, exhibits a closed 

 cylinder of vessels. Sometimes this condition is found only 

 in one longitudinal moiety of the stem, whilst in the 

 other the distribution of the meshes of the vascular bundles 

 is the same as in the neighbourhood of buds. Roots — re- 

 markable for the slight development of the root-cap — spring 



* The canal is somewhat enlarged above the punctum vegetationis. 



