cn. II. 



COUKSE OF THE SAP. 



71 



I think the case deserves investigation. I also think 

 that such a question as this being hitherto unansLoered — 

 (might I not say, hitherto unasked f) — ^proves that we 

 have yet much to learn in the science, and that there 

 are many things under heaven and earth little dreamt 

 of in our ^physiology.'' Unless these concentrical piths 

 are piths, the growth of the bud, when disconnected 

 from the central pith below it, disproves De CandoUe's 

 ingenious suggestion, that the pith is the cotyledon of 

 the hud: for the life of the seedling is dependent on its 

 cotyledon, — that is, on its seed ; and it perishes when 

 disconnected from it, even after leaves are developed 

 on the plant, and the roots are several inches long. 

 But besides this, the cotyledon, or seed, is absorbed 

 and vanishes in feeding the seedling, but the pith 

 endures for ever. De Candolle states that, in the 

 chestnut, the ash, and the vine, ' the pith is interrupted 

 at each node, or annual shoot, by a kind of ivoody par- 

 tition.' Here, I think, this very great physiologist 

 makes a very great mistake. It is true, that in the 

 ash and horse-chestnut, at the junction of one year's 

 shoot with the next, the texture of the pith may be 

 described as cheesey.^ instead of spongy. And in the 

 vine, this cheesey pith separates the spongy pith, not 

 only at the junction of each annual shoot with the 

 next, but at each knot or side-bud. But there is 

 nothing in the least resembling wood in this cheesey 

 pith ; and when it is scooped out, the pith- channel of 

 the vine is of the same size through the knots as at 



