PROPERTIES OF BARK. 631 



commercially. In conifers, turpentine is elaborated, partly in 

 the interior of the parenchymatous cells, where it continually 

 increases (resin-cells), partly in spaces (resin-ducts) between 

 closely-packed parenchymatous cells. The outer bark possesses 

 only vertical resin-ducts, the inner bark only horizontal ones, 

 which are continuations of those in the medullary rays of the 

 wood. 



The dead bark, or rhitidome, arises from the above cell- 

 forms by the scale-like formation of cork ; rapid growth in 

 thickness, warm localities, insolation, open crop of trees, tissue 

 tension at the base of branches, etc., favour the early forma- 

 tion of rhitidome and the scaling off of bark (*). At the 

 junction of the inner bark of the wood is the cambium, 

 which forms outwardly the organs of the inner bark. The 

 bark of monocotyledonous woody species, such as palms and 

 bamboos, is confined to a few layers of cells, under which, 

 without any canibium, lies the so-called wood, resembling pith, 

 but traversed by strands of wood. The superficial cells are 

 strongly silicified ; there is no formation of cork. 



SECTION II. CHEMICAL, PHYSICAL AND ECONOMIC PROPERTIES 

 OF BARK AND OF ITS CONSTITUENTS. 



For the sake of brevity the above will be discussed together 

 with the utilization of the bark. 



1. ProjH'rties, Utilization, Valuation and Disposal of Bark. 



The young green bark of our woody species has little 

 durability ; as a rule, in the first or second year the green 

 colour is lost when cork is formed, so that reddish, yellow, 

 brown or grey tints prevail. In using saplings of oak, dog- 

 wood, hazel, etc., for walking-sticks or umbrella-handles, the 

 colour, lustre and scent of the bark are important. In species 

 of palms and bamboos, the external bark becomes in time 

 very durable owing to its gradual silicification. The rind of 

 bamboos is coloured most variously, according to the species 

 and variety of the plants ; it has yellow, brown or black specks 

 or stripes, which render bamboos attractive as fishing-rods, 



* H. Mayr, "Die Sekretionsorgane der Fichte urid Liirche." Bot. Zentral- 

 blatt, 1884. 



