LETTER XIV. 



151 



other buds, although from the cause mentioned 

 their shoots are small or but imperfectly developed.* 

 The phenomenon is best exhibited, in those trees 

 that admit of it, after the trunk has been cut 

 close to the ground, when large and vigorous " suck- 

 ers " spring from the stump, and even from the 

 roots. 



8. What passes, then, from the leaves into the 

 stems and trunk appears " certainly," from what we 

 have seen in this and the preceding letter, to be 



descending matter." Nor is it elaborated " sap 

 merely which passes down, — but woody tissue also. 

 However paradoxical it may seem, this tissue is at once 

 formed in situ and by growth downwards. Ordinarily, 

 it does not actually creep downwards from the top to 

 the bottom of a tree. It has no need to do so. Yet 

 even then it does so virtually. And when occa- 

 sion requires or opportunity offers it does so in 

 reality. Let me recall to your recollection the leading 



* These Cambium-buds commonly undergo imperfect develop- 

 ment — often evolving externally little else than leaves or leaflets, 

 but reproducing themselves and vegetating year after year at the 

 same points, give rise to nodosities or swelUngs (v^hich often attain 

 a considerable size) on different parts of the trunk of many trees. 

 I am inclined to think that a close inspection of these nodosities 

 would shew that they are chiefly accumulations of woody tissue 

 evolved from the leaflets of those buds; and if so, the fact would 

 furnish another argument, and be a peculiarly valuable addition to 

 the evidence already adduced, in favour of the doctrine contended 

 for in the text. 



