THE FUNDAMENTAL SYSTEM. 



137 



(6) Ordinary herbaceous Dicotyledons furnish the best examples of 

 fully developed fundamental tissues ; tliey can be most easily exam- 

 ined after soaking for some time in alcohol. 



(c) Examples of thin-walled cork are, of course, best obtained from 



Fig. 113.— Transverse section through a lenticel ot Beiula alba, e, e, epidermis ; s, 

 old stoma ; under this is a mass of corlc which develops from the phellogen layer 

 lying next to the ordinary parenchyma (figured darker) ; the great multiplication of 

 cork-cells has pushed out the epidermis, x 28U.— After De Bary. 



the ordinary commercial article ; the thick-vvalled form may be obtained 

 from the bark of the beech, willow, prickly ash {Xanthoxylum Amer- 

 icanum). Viburnum opulus, etc. Its development may be observed by 

 making successive sections of the shoots at different heights. 



