CHAPTER II. 



SCLERENCHYMA. 



Sect. 28. The name Selerenchyma, introduced by Mettenius\ here indicates 

 those tissue-elements which have not only thickened their walls at the expense of the 

 cell-cavity, but have also lost the cell quality besides. Together with the sclerotic 

 cells of- the foregoing paragraphs they form the strengthening apparatus. But while 

 the former, by reason of the nature of their contents, still take an active part in the 

 processes of assimilation and nutrition, the properties which point to this are wanting 

 in the tissues in question ; they appear (besides some connection with the transfer of 

 water) to be in the main only strengthening apparatus, or specific mechanical 

 elements, to use the terms of Schwendener. 



We will not here again return to the practical difficulties in distinguishing this 

 tissue from the sclerotic cells. Comp. p. 115, and Chap. X. 



The general properties of the sclerenchymatous elements consist in this, that as 

 the thickening and lignification proceed, the protoplasmic body and nucleus dis- 

 appear, and of these and of the products resulting from their activity only remnants 

 together with watery fluid remain behind, partly as not clearly defined granular 

 contents; often however they take the form of rather abundant fine-grained 

 starch, which apparently has no further use, as e. g. in the fibrous ring of the 

 outer walls of Aristolochia Sipho, or of crystals of Calcium oxalate, as in many 

 covering tablets of fibrous bands, to be described below, and in the raphide- 

 containing fibres of the cortex of the root of Chamoedorea elegans. According to 

 Schwendener ^ a part of the fluid contents is replaced in the typical sclerenchymatous 

 fibres by air ; they always contain some air in the normal condition. The structure 

 of the walls is in general that of strongly thickened cell-membranes, with their 

 numerous modifications : these will be more readily described in connection with 

 the single forms. 



According to the form, and the definite relations of structure which vary for the 

 most part with it, w^e may distinguish two main forms of sclerenchymatous elements, 

 which, however, are not in all cases sharply defined from one another, viz. (i) short 

 sclerenchymatous elements, and (2) elongated elements, or sclerenchymatous fibres. 



* Abhandl. d. K. Sachs. Ges. d. Wissenscli. IX. p. 432. 



• Das Mechaiiische rrincip, &c., p. no. 



