164 



PHYSIOLOGICAL BOTANY. 



sues composed of the cells, vessels, and ducts which 

 have already been described. 



416. The bark at the end of the first year's growth 

 is made up of three layers : the one next the wood, 

 called bast, is composed of pa- 

 renchyma, sieve vessels, and li- 

 ber-cells ; on account of the pre- 

 dominance of the bast ducts in 

 this layer, it has been called the 

 last region (Figs. 508, 516). 

 The liber-cells are long, strong 

 fibers, and in some plants are 

 very tenacious and flexible, form- 

 ing the material in Hemp, Flax, 

 and other textile substances util- 

 ized in manufacture of cordage 

 and fabrics. 



Next to the bast is the green 

 cellular layer, called phellogen, 

 because by its dividing, it pro- 

 duces outside of it cork, which 

 increases by the addition of new 



material to the inner surface. ^_^_ 



The cork is usually of a brown 



.516, Is a photograph from nature of a 



or ashv color, sometimes white layer of bast-fibrous bundles found in the 



secondary bark of the' stem of an old Carica 



or striped ; in old trees it is IGtfSZ^Stt&Z 

 cracked and broken by the KLTG^S-JJSSJ 



o-TTkAxrtVi rf fVifi ASrnorl nnH fflllQ have formed an irregular net- work with 

 giOW til Ul LI1U WUUU, c elongated sinuous meshes. These meshes 



off in scales or strips, as in the J^S^'tJSJ^^SS 1 !! 

 shag-bark Hickory ; in the Paper moved by maceration ' 

 Birch it peels off in sheets resembling paper. Upon 

 some trees it develops into thick porous layers, and 

 upon the Cork Oak furnishes the cork of commerce. 



