62 Eug. Warming. 



presque perpendiculairement en suivant la tige a laquelle elles 



se trouvent parfois accolées au debut. Ce n'est qu'a la base 



inférieure de la tige (voir fig. I), ou bien sur de vieux trones 



dont les restes de galnes foliaires externes ont disparu, que 



ces racines, auxquelles j'applique le qualificatif d'intervapinales, 



font leur apparition. 



Cette singuliére disposition n'est pas inconnue, quoique 



nulle part parait-il, dans la littératnre speciale moderne, elle 



n'ait été signalée. Dans son «Introduction to Botany« (1839) 



p. 315, Lin die y la mentionne chez un Barbacenia et en donne 



une description claire et tres exacte comme la citation ci-contre 



en fait foi: 



«In an unpublislied species of Barbacenia from Rio Janeiro, 

 allied to B. purpurea, tbe stems appear externally like those 

 of any otber rough-barked plant, only tbat tbeir surfa.ee is 

 unusually fibrous and ragged when old, and closely coated by 

 the remains of sheathing leaves when young. Upon examin- 

 ing a transverse section of it, tbe stem is found to consist 

 of a small, firm, pale, central circle baving tbe ordinary endo- 

 genous organisation, and of a large number of smaller and very 

 irregular oval spaces pressed closely togetber, but baving no 

 organic connection ; between tbese are traces of a cbaffy ragged 

 kind of tissue, which seems as if principally absorbed and des- 

 troyed. A vertical section of tbe thickest part of tbis stem 

 exbibits, in addition to a pale, central, endogenous column, 

 woody bundles crossing each other or lying parallel, after the 

 manner of the ordinary ligneous tissue of a Palm stem , only 

 the bundles do not adhere to each other, and are not embodied, 

 as usual, in a cellular substance. Tbese bundles may be read- 

 ily traced to tbe central column , particularly in the younger 

 branches, and are plainly the roots of the stem, of exactly the 

 same nature as those aerial roots which serve to stay the stem 

 of a Screw Pine [Pandanus). When they reach the earth , the 

 woody bundles become more apparently roots, dividing at their 

 points into fine segments , and entirely resembling on a small 

 scale the roots of a Palmtree. The central column is much 

 smaller at the base of the stem, than near the upper extremity. 

 Nothing can well show more distinctly than this tbat the woody 

 bundles of tbe endogenous stem are a sort of roots emitted 

 by the leaves, plunging down through their whole length jjnto 

 the cellular substance of the stem in ordinary cases; but, in 

 Barbacenia, soon quitting tbe stem, and continuing their course 

 downwards on the outside.» 



