A PROPOS 

 DE L'ÉPIDERME FOLIAIRE DE BETULA 



PAR 



M. leOLIBlEU 



Communiqué en séance du 13 février 1911 



Dans uiu' étude de géograpliie botanique publiée en décembre 

 dernier/ W. et G. -S. West touchent à un point de l'anatomie foliaire 

 de Betnla, niais en coniniettaid une erreur si manifeste et si impar- 

 donnable, que je me vois obligé de la relever. 



Voici textuellement le passage incriminé : 



« One character, possessed by ail tbe leaves oUietula natta examined, 

 irrespective of altitude, is tbe présence of an incomplète layer of liypo- 

 dernial cells beneatb tbe upper epidermis. Tbis layer is derived from 

 theupper epidermis, tbe cells ofwbicb are of \ariable size. Tbeir outer 

 walls are more or less plane, wbereas tbeii' iuner walls are very 

 convex and quite connuonly bemispberical. Tbey are also of very 

 variable deptb. Tbe majoritV of tbese cells are divided by a wall 

 pai'allel to tbe surface of Ihe leaf and nearer tb(> outer tbnn tbe inner 

 ^vall. 



« Tbus, a relatively large bypodermal cell bas been eut oll trom a 

 narrower epidermal cell. tbe dividiiig-\\all and tbe otber walls of tbe 

 bvpodermal cells are exceedingly tliiu, \\ itb a still Ibinnrr liniiig proto- 

 piasiuic laver, tbe iuterior of tlie cell being occupied by a colourless 

 cell-sap vacuole. Tbe outer walls of tbe epidei-nial cells are fairly strong 

 and well cutinized. Sucb a bypodermal layer does uot appcar to bave 

 been observed in species of Beliila, allbougb a uumber of species of 

 Alnus possess a bypoderma. 



« Tbe bypodermal cells of /k'Iula nana are boib conspicuous and 

 irregular, tbe palisade cells extending upwards and lilling u}) tbe irre- 

 gularities. Tbe walls are so délicate and tbe vacuoles so completely 

 îill tbese cells, tbat we can only regard tbem as constituting a sligbt 

 development ofaqueoustissue. U sbould be reniarked tbal /U'Iiila nuiia 

 grows for tbe most part in very exposed situations, wbere it is subject 

 to almost conlinuous \\iuds. » 



W. et G. -S. West disent donc avoir constaté cbez lietitla la |)i-ésence 

 d'un bypoderme, provenant d'une division tangentielle de l'épiderme. 



' W. aiul G.-S. West. — Tlie Ecology of the Upper Driva Valley in the 

 Dovrefjeld. (T/ie New Phytologist, vol. IX, no 10, déc. 1910, p. 36o-366, fig. 28). 



