130 VEGETABLE SAP. 



above it. Besides, if this downward motion be only 

 that of an effect on the cellular structure, why should 

 a bandage prevent the expansion of the structure of 

 the stem, as well below as above the band? 



The subject is every way intricate, and requires 

 investigation. We have made many experiments to 

 ascertain the cause, but without success. All our 

 conclusions have been negative rather than affirma- 

 tive of what we expected what it is not, rather than 

 what it really is. For instance, we observe that the 

 new zone of wood formed in the course of summer, 

 begins to be visible at the bottom of a lofty tree 

 nearly as soon as it is on the highest branches, though 

 we cannot vouch for its being as soon perfect. This 

 being the case, we doubt whether any fibres specially 

 attached to, and descending from, the expanding buds 

 and lengthening shoots, can possibly reach so far 

 down the trunk in so short a time as elapses between 

 the bursting of the buds and appearance of the new 

 alburnum so far below ; nor can we admit that there 

 is any gradual descent of fibres in the course of 

 several years that is those belonging to the buds 

 of 1827 gaining, or reaching to the base of the trunk 

 in 1831, or in any subsequent year. We know this 

 to be impossible, as will appear by referring to Fig. 

 48, page 145. Another thing the longitudinal connec- 

 tion and arrangement of the fibrous structure of each 

 zone of wood, is so entire from top to bottom, that, 

 on examination, we can arrive at no other conclusion 

 than that the whole is simultaneously produced. 



