1034 



their walls, next proceeds to explain the descent and ascent of elabo- 

 rated sap. 



" Experiments performed upon Living Plants, with a view to de- 

 termine the Passages which convey the Elaborated Sap. — 29. In the 

 winter of 1844, three suckers of lilac, of two years' growth, all spring- 

 ing from the same root, were severally girt with a piece of copper 

 wire, drawn as tight as it would admit of without cutting into the 

 bark, and the eflfect was carefully watched until the spring of 1847. 



" 30. In the spring of 1845 it was observed that the budding com- 

 menced at the same time in these suckers as in some others growing 

 from the same root ; and that during the summer and early part of 

 the autumn no difference could be distinguished in the state of the 

 vegetation of these shoots, the girt always appearing as healthy as the 

 ungirt ones. In the winter, one of the girt suckers was cut for the 

 purpose of examination ; the other two were allowed to remain. 

 The part of this sucker above the ligature had received a layer of new 

 wood of the ordinary thickness, also an addition to the bark : that 

 included in it retained of course its former diameter, but had under- 

 gone an alteration, a thin layer of wood having been added to that of 

 last year, and the bark having become thinner than it was before, in 

 consequence of being compressed between the new wood and the 

 ligatux'e. The part below the ligature was smaller than that above, and 

 had received a new layer both of wood and of bark, but both much 

 thinner than those above the ligature. In the immediate vicinity of 

 the wire the shoot was swollen both above and below, but more so 

 above than below. 



"31. In the spring of 1846, the two constricted suckers which re- 

 mained were observed to begin budding at the same time as some 

 other suckers growing from the same root; and during the spring and 

 summer no very material difference could be distinguished in their 

 states of vegetation. The leaves of the constricted suckers appearing 

 perhaps a little yellower than those of the unconstricted ones, but in 

 all other respects they had the same aspect. The part of the stem 

 close to the ligature was swollen both above and below it ; and 

 although the stem above the wire had increased considerably in 

 diameter, the part below it had undergone no increase in thickness. 



" In the early part of the summer, one of these suckers was cut and 

 examined with the microscope, but the other was allowed to remain 

 for future observation. The part of this sucker above the ligature had 

 received a layer of new wood, also an addition to its bark : that in- 

 cluded in it had undergone a change similar to the one mentioned in 



