228 EXPERIMENTS WITH PLANTS 



up the stem, we notice that it travels much faster in 

 these ducts than in the other parts of the wood. 

 Between the ducts is a mass of smaller cells, which 

 also become colored by the liquid after a time and 

 which appear therefore to assist in conveying water. 



Having made out these points, we may take from 

 the cut surface of the stem, by means of a razor 

 moistened in water, the thinnest possible slices (when 

 thin enough they are almost colorless and will sink in 

 water ; in this way they may be separated from the 

 thicker ones). Transfer them (by means of a camel's- 

 hair brush dipped in water or the point of a knife) to 

 a glass slide, and cover with a cover-glass. Examine 

 first with the low and then with the high power of the 

 compound microscope. 



Let us now cut the stem lengthwise in such a way 

 as to divide a bundle lengthwise into two halves in a 

 plane passing through the center of the stem. From 

 one of the cut surfaces take sections (thin enough to 

 be translucent), place them (without water or cover- 

 glass) on a slide, and examine with the low power. 

 We now see that the bundle consists of a mass of elon- 

 gated tubes packed closely together, the central portion 

 of which, the wood, is conspicuous by the red colora- 

 tion due to the eosin ; the ducts are very conspicuous 

 by reason of their large size. 



Let us now cut much thinner sections from a cut 

 surface prepared in the same way, mount them in 



I 



