154 



PHYSIOLOGICAL VIEWS. 



Fig. 94. The wood is divided into fibres run- 



ning longitudinally through the 

 stem ; (see 94, where the dots re- 

 present the fibres ;) each of tin -so 

 fibres seems to vegetate separate- 

 ly; they are ranged around a cen- 

 tral support ; and are so disposed 

 that tin; oldest are crowded out- 

 wardly by the xlevelopement of 

 n u fibres in the centre of the 

 stem ; this pressure causes the ex- 

 ternal layers to be very close and 

 compact. This mode of increase, 

 little favourable to growth in diameter, produces long and 

 straight stems, which are nearly uniform in their size throutrh. 

 out their whole extent ; as the palms and sugar-canes of the 

 tropics, and the Indian corn of our climate. Most of these 

 plants present us with roots of the fibrous kind. 



a 



Fig. 95, at A, represents a section of the stipe or stem of a 

 palm tree ; at B is the same magnified ; a b, a part of tho 

 stipe in which the woody fibres are most dense and hard ; b c, 

 shews the fibres less numerous, less compact, and less hard ; 

 c d, the woody fibres, tender and scattered ; we here see tho 

 orifices of tubes, which have disappeared, at c a. In the part 

 c dj the cellular tissue occupies a greater space than at c, b t 

 and much more than at b a, where the woody fibre or vascu- 

 lar texture predominates. The fibres at e, are of new forma- 

 tion ; atf they are older, and at g still more ancient ; thus the 

 developement of the wood proceeds inversely to that of dico- 

 tyledonous plants. 



Formation of epidermis Deicribe a monocotyledonous or endogenous stem. 



