METABOLIC PROCESSES IN THE PLANT. 343 



berbsrin. Berber! 11 is also found in the peripheral part of the 

 wood (viz., as a deposit in the membranes). 



On treating the sections with alcohol and very dilute Nitric 

 acid (1 part of Nitric acid to 50 parts of water), the yellow colour 

 disappears from the berberin-containing elements. The presence, 

 however, of large quantities of berberin now causes the separation 

 of yellow crystals of Berberic nitrate. 



We prepare delicate transverse or longitudinal sections from a 

 corm of Colchicum autumnale. In the immediate neighbourhood 

 of the vascular bundles we observe cells which contain a strongly 

 rcfringent yellowish fluid, while the main mass of the parenchyma 

 is very rich in starch. These yellow cells contain colchicin. On 

 treating the sections with ammonia, their contents take on an 

 intensely yellow coloration. The roots of Colchicum contain 

 colchicin in the epidermis and the protective sheath. 



In the stem of Aconitum Napellus, aconitin is found in the 

 vascular bundle sheath and in the parenchyma in its neighbour- 

 hood. Aconitin gives with iodised Potassium iodide solution a 

 brownish-red precipitate ; and with Sulphuric acid diluted with 

 ^-J its volume of water, especially if the preparations have 

 previously been treated with cane-sugar solution, it gives a 

 carmine red coloration (Errera). 



If transverse sections from twigs, about 3 mm. thick, of Syringa 

 vulgaris are mounted in dilute Sulphuric acid (1 part by volume 

 of concentrated Sulphuric acid and 2 parts by volume of 

 water), the membranes of the wood elements, of the medullary 

 rays in the wood, and of the bast fibres colour yellowish green, 

 and later bluish green. All the other cells remain uncoloured. 

 The reaction in question is caused by the presence of syringin. 

 This substance is deposited in the membranes. Sometimes, also, 

 the contents of the cells of the cortex take on a bluish colour 

 when sections of Syringa are treated with Sulphuric acid ; but 

 this is merely due to some of the syringin having diffused into 

 these cells in the course of the reaction. 



We prepare transverse sections from twigs of Rhamnus 

 Frangula, about 3 mm. in diameter, and treat them on the slide 

 with an alcoholic solution of Potassium hydrate. Various ele- 

 ments of the sections, especially the thin- walled elements of the 

 bast, become intensely red in colour, the coloration being, how- 

 ever, not very stable (frangulin reaction). 



In transverse sections from the root of Rumex crispus, we shall 



