WORK OF THE SHOOT 89 



Currents in the stem. Let us now perform a few experi- 

 ments which will enable us to determine the channels 

 along which travel the materials used by the shoot. 



Place in a bottle red ink or a solution of eosin, and obtain 

 shoots of Rhododendron, Ivy, or similar evergreen. Place 

 the freshly-cut ends of the shoots in the coloured solution. 

 From one of these, and above the level of the solution, 

 cut a broad ring of tissue into the wood. Place a similar 

 shoot in another bottle, but instead of eosin, use water to 

 which a little finely-powdered carmine has been added. 

 The particles are exceedingly minute and of such a nature 

 that they remain in suspension a long time and produce 

 a coloured liquid. Leave these for a day or two and then 

 compare them. Are they equally fresh ? Is there any 

 difference in colour in the shoots ? Cut short pieces from 

 the lower end of each and compare the cut surfaces. How 

 do they differ ? Cut off a piece two inches long and split 

 it longitudinally down the middle. Is the stem uniformly 

 coloured ? Are the shoots coloured similarly ? Scrape off 

 some of the bark and determine which tissue is coloured. 

 Trace this coloured tissue upwards and determine whether 

 it extends into the leaves. Cut the leaf-stalk and leaves 

 across and note whether they are coloured ; and, if so, how ? 



What do we learn from these experiments ? We find 

 that the shoots in eosin have taken up the coloured solu- 

 tion, and it has ascended only through the woody portions 

 of the stem and leaves, and not through the bast, cambium, 

 cortex, or epidermis, for in the shoot from which these 

 tissues have been removed the eosin has ascended, not- 

 withstanding their removal. The shoot in carmine, 

 however, remains uncoloured. Why ? Here the fine 

 particles of carmine are in suspension, not in solution, 

 and although a coloured solution like eosin may be 

 absorbed, the particles, even so fine as those of the 

 carmine, are unable to pass through the woody tissues. 



