PARENCHYMA. ENDODERMIS. 



133 



of Botrychium Lunaria. In the root of Ranunculus Ficaria Caspary found most 

 of the cells suberised, more particularly at least on the undulated walls ; and, on the 

 other hand, single cells, with no exactly definable arrangement, equally suberised all 

 round. The walls in question may be termed suberised on this ground, viz. that 

 they behave before reagents like the totally suberised membranes of the cork-cells, 

 or like cuticle. (Comp. pp. 75 and rii.) They alone remain behind after the 

 action of concentrated sulphuric acid, even if the acid has destroyed the surrounding 

 cellulose walls. More exact investigations of its chemical relations are entirely 

 wanting. Further, the peculiar refractive properties of corky walls, the dark black 

 contours when seen by transmitted light, belong to the walls in question. Partly in 



FIG. 49.— Ranunculus fluitans : transverse section through the vascular bundle of a strong old .adventitious root (225), 

 u endodermis, / per icambium, pouter primordial vessels of the diarcli uniseriate xylemi'— ^; between^— i' and j* the phloem. 

 Fig. 50. — {37s) A piece of the endodermis in tangential longitudinal section. 



this circumstance, partly in the wavy folds superposed one on another, in not very 

 thin preparations, lies the cause of the often-described phenomenon, that the un- 

 dulated strips of the radial walls appear in transverse sections as dark points or lines. 

 Another peculiarity, which again recalls the cuticle, is this, that the suberised parts 

 of the walls swell in sulphuric acid and in potash in the direction of their surface. 

 The undulations appear after the action of those . reagents to become higher ; but 

 whether this is really the case, or whether they only become plainer for observation, 

 remains to be investigated. 



Like many cork-cells, those of the endodermis often remain thin-walled through- 

 out life, e. g. in almost all Ferns, the walls being either totally suberised, or (a point 

 which requires more extended investigation) having a delicate internal cellulose 

 layer. But on the other hand, there appears not infrequently here also a strong 

 thickening superposed internally on the original membrane : this occurs especially 

 in roots of Monocotyledons, the stems of Potamogeton (in many species, as 



