158 



XI. THE DICOTYLEDONOUS STEM WOODY TYPE. 



us the same elements as in the radial section, but the medullary 

 rays are cut in section, and from this point of view appear 

 spindle-shaped (r). They are of very various heights, and may 

 be unilamellar through their whole height, or multilamellar in 

 the middle. The intercellular spaces are almost completely 

 wanting at the sides of the unilamellar medullary rays ; in the 

 multilamellar they are only formed between the inner cells. The 

 tangential longitudinal section through the bast shows as far as 

 the medullary rays are concerned the same relations, and can 



also serve, just like the tangential 

 section of the wood, to demonstrate 

 to us the serpentine course which 

 must be taken by the elements 

 which are' displaced by the medul- 

 lary rays. 



Chlorzinc iodine stains the lig- 

 nified tissue yellowish- brown, the 

 cambium violet. In the bast is 

 shown a beautiful alternation of 

 the violet thin- walled zones, and 

 the bright yellow thick- walled bast- 

 fibres. The elongated medullary 

 rays of the primary cortex are 

 violet, the cork is reddish- brown. 

 Corallin stains the wood cherry- 

 red, the bast-fibres quite a strikingly 

 beautiful bright rose - red. The 

 sieve-plates stand out clearly, even 

 in the cross-section, by their foxy- 

 red colour. 



Isolation of Tissue-elements by 



Maceration. It is always a matter 



J 



FIG. 62. Tangential longitudinal of some difficulty for the beginner 

 section of the wood of TO^; pitted t fc t ith accuracy the 



duct ; t, spirally-thickened tracheide ; J 



p, wood-parenchyma ; I, wood-fibre ; individual components of COmpli- 

 r, medullary rav(x 160). , , 



cated structures, such as are shown 



in longitudinal sections through the wood, particularly of second- 

 ary wood ; and we will endeavour to supplement our knowledge 

 by using another method, the so-called Schultze's treatment by 

 "maceration". For this purpose we place in a wide test-tube 

 a few crystals of chlorate of potash, and pour in enough nitric 



