THOSE LITTLE WORKSHOPS 79 



not across it. Such tubes have been named " channels " 

 and " water-pipes " and " water-mains," because of the 

 quantities of water filtering through them. 



In a tree which has begun its growth with two small 

 seed-leaves these delicate water-pipes lie chiefly between 

 the bark and the wood. But in a tree which has begun 

 its growth with only one small seed-leaf they run 

 throughout the whole trunk. 



It was argued that the sap, reaching each of these 

 tubes in turn, would be naturally drawn upwards by 

 this particular kind of attraction, which is known as 

 " Capillary," from the Latin word for " hair." Each 

 of our hairs is really a tiny hollow tube. But though, 

 no doubt, there is truth in the explanation, it is not 

 enough by itself, not nearly enough, to account for the 

 mystery. 



II OTHER SUGGESTIONS 



A different idea, more lately put forth, is less easy 

 to make clear. It has to do with the " make " of the 

 cells and tubes of a tree. 



Both cells and tubes, little round cells and long slim 

 tubes, are clothed in a most fine and delicate skin, 

 which is called by the same name as the thin outer skin 

 of our bodies the " cuticle." And the tubes are not 

 open at either end like a glass tube. All these cells and 

 all these tubes are closed at both ends. 



As the sap rises in the tree it has to make its way 

 right through this skin before it can go from one cell or 

 one tube to another. It finds no tiny open doorways. 

 The whole tree-trunk is divided into millions and 

 millions of little compartments, and in every few feet of 



