III. THE LEAF. 53 



believe all the charcoal they want, and most of 

 the water, from the air. Now the question is, 

 where and how do they take it in, and digest it 

 into wood? 



14. You know, in spring, and partly through all 

 the year, except in frost, a liquid called 'sap' circu- 

 lates in trees, of which the nature, one should have 

 thought, might have been ascertained by mankind 

 in the six thousand years they have been cutting 

 wood. Under the impression always that it had 

 been ascertained, and that I could at any time know 

 all about it, I have put off till to-day, 19th October, 

 1869, when I am past fifty, the knowing anything 

 about it at all. But I will really endeavour now 

 to ascertain something, and take to my botanical 

 books, accordingly, in due order. 



(1) Dresser's "Rudiments of Botany." 'Sap' not 

 in the index ; only Samara, and Sarcocarp, — about 

 neither of which I feel the smallest curiosity. 

 (2) Figuier's " Histoire des Plantes."* 'Seve,' not in 

 index ; only Serpolet, and Sherardia arvensis, which 

 also have no help in them for me. (3) Balfour's 

 " Manual of Botany." ' Sap,' — yes, at last. " Article 

 257. Course of fluids in exogenous stems." I 

 don't care about the course just now : I want to 

 know where the fluids come from. " If a plant be 

 * An excellent book, nevertheless. 



