1:^0 



PLANT ANATOMY* 



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she the cork of commerce. 



In many plants the phellogen layer 

 makes an inner periderm as well as the 

 outer one of cork; this is the case in 

 Althaea, Glycyrrhiza, Ipecacuanha, Lev- 

 isticum, Rhatany, Angelica, Senega, etc. 

 In the inner periderm, whether of phello- 



T 



1 



w- 



Fig. 34.— Glandular hair from leaf of Hyoscy- 

 amus niffer. (Tscliirch). 



cells that aid in the formation of new 

 cells, and the product of the meriste- 

 matic tissue, namely, the cork. 



The meristematic layer is termed the 

 Plielloi^en Layer, and has its ori^nn iu 

 the paronehymatic cells that lie just be- 

 neath the epidermis. These cells divide 

 by tauffontial cross walls, the inner prod- 

 ucts of the division retaining the power 

 to divide, while the outer products be- 

 come cork cells, 



Cork Cells are "generally thin-walled 

 and quite regular in shape, having the 

 form of flattened tablets. They are 

 brownish-red in color and give the char- 

 acteristic reactions of suberin. The con- 

 tents are mainly air, but often various 

 ?olorin£: matters are found giving the 

 2ork its peculiar color. Although typi- 

 cally thin-walled, the cork colls inay 

 have thickened walls which may become 

 hard and stony as seen in the plane tree. 

 Cork cells vary in their number of lay- 

 ers from one cell deep, in the potato, to 

 many feet in thickness in the oaks that 



Fiff. 3o.— Cross section of young shoot of Cin 

 chona Cali^aya. showing the beginning of the 

 I'enderm. k phellogen layer forming cork. « 

 epidermis with hairs still present, mr primary 

 rind, ^mucilage reservoirs: ad sieve tubes in the 

 secondary cortex, c cambium, mk medullar> 

 ray>. m pith. (i&L-hiiCtj;. 



