CHAPTER XIV. 

 CORK LENTICELS BARK. 



PRINCIPAL MATERIALS USED. 



Normal twigs of Sambucus nigra (Elder), still green; also similar twigs 



becoming, and become, grey ; fresh, also in alcohol. 

 Old twigs of Cytisus Labttrnum ; in alcohol. 

 Fine bottle corks. 



Old twigs of Ribes rubrum (Red Currant) ; preferably fresh. 

 Potato tuber ; fresh. 



PRINCIPAL REAGENTS USED. 



Concentrated solution of chlorophyll, freshly prepared Solution of alkanet 

 in 50 per cent, alcohol Fuchsin Absolute alcohol Chlorzinc iodine 

 Potash Concentrated potash Chlorate of potash and nitric acid. 



WE have already, upon various objects, had the opportunity of 

 becoming acquainted with the position and structure of cork, 1 but 

 will once more turn our attention to this tissue, in order to study 

 on the one hand the Lenticels, and on the other hand the struc- 

 ture and reactions of the membrane of the cork cells. 



Cork of Sambucus. Cross- sections through a twig, still green, 

 of Sambucus nigra (the Elder) show us, around the broad large- 

 celled pith the separate vascular bundles already connected into a 

 ring by the action of the interfascicular cambium. The cambium 

 ring has also already commenced its activity, and in the vascular 

 bundles, as well as also between them, has formed secondary 

 wood and secondary bast. The primary bast appears supported 



1 Many rapidly-growing stems of woody plants show the development of 

 cork with remarkable beauty. Amongst the best are species of Hibiscus and 

 Abutilon, very commonly cultivated hot-house perennials. Fresh or in alco- 

 hol. In Sambucus nigra it is necessary to avoid the stout succulent shoots 

 which are often met with, and to select only the thin normal growths. [ED.] 



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