CHAPTER X. 



ARRANGEMENT OF THE SCLERENCHYMA 

 AND SCLEROTIC CELLS. 



Sect. 124. As shown by their anatomical characteristics, and as Schwendener 

 has demonstrated, sclerenchyma and sclerotic cells form the strengthening apparatus 

 of the plant ; the former is specifically and almost exclusively adapted to the 

 mechanical function mentioned, the latter serves other functions simultaneously in 

 different degrees ; the two are connected one with another by various transitional 

 forms. Accordingly they may both bear a common name, viz. stereides, or steren- 

 chyma ; and the groups they form may with Schwendener be termed stereome. The 

 collenchymatous masses also are immediately related to the sterenchyma as transi- 

 tory strengthening apparatus which often passes over into sclerenchyma, and hence 

 we must often take them into consideration in treating of the latter. The same ap- 

 plies to sclerotic endodermal layers, which have been discussed in former chapters. 



Schwendener, in his excellent work which has been so often mentioned', has 

 treated both the arrangement of the sclerenchymatous masses and their physiological 

 relations so minutely and comprehensively, that any detailed exposition of the former, 

 within the space here available, must be a mere extract from his work, or must seem 

 like one. I therefore think it best to refer once for all to the book mentioned, 

 merely giving short indications respecting the masses of sterenchyma which serve to 

 strengthen entire organs, as stems, petioles, &c., and only entering more minutely 

 into some of the points which have received less attention In Schwendener's work. 



In the vegetative organs of the Phanerogams, to which, among the groups of 

 Filicinese, the Equiseta and the non-aquatic species of Isoetes are in this respect 

 especially related, the sclerenchyma is usually more sharply differentiated throughout 

 than in the majority of the Ferns. The latter may therefore be treated subsequently 

 by themselves, and for the present be left out of consideration. 



Sect. 125. Sclerenchymatous fibres, or sclerotic elongated cells which 

 approach them very nearly, occur generally in parts which are exposed to bending or 

 tension, and are united to form strands, layers, or sheaths, which traverse the entire 

 organ longitudinally. 



As regards their arrangement, we find in the first place strands and layers in 

 the hypodermal region, partly in direct contact with the epidermis, partly separated 

 from it only by one or a few layers of cells. It is a phenomenon of wide occurrence 



' Das mechanische Princip, &c., Leipzig, 1874. [See also Haberlandt, Entwickelungsgeschichte 

 des mechanischen Systems; 1879. — Westermaier, Z. Kenntniss des Mechan. Gewebesystems ; Bot. 

 Ztg. 1882, p. 174.] 



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