372 Dr. Lankester^s Remarks on Du Petit Thouars's 



been cut down. During the early part of this summer I found 

 upon the stems of several elm trees that had been cut down a 

 development of hard new matter between the bark and the 

 wood of the tree : on submitting portions of this secreted mat- 

 ter to the microscope, I saw distinctly delicate fibres running 

 in the direction of the fibres of the bark and wood. On the 

 stumps of the trees on which this matter was found there were 

 no branches or buds ; and as the stems had been removed the 

 preceding year, these fibres must have been formed inde- 

 pendent of either buds or leaves. 



In order to satisfy myself of the correctness of these obser- 

 vations on the exudation of wood from the stumps of trees, in 

 the latter end of the month of March of this year, I cut away 

 an entire ring of bark about an inch in length from the 

 branches of several young beeches. At this time the sap was 

 rising and the bark was easily removed from the alburnum on 

 which it lay. On the 6th of this month (Aug. 1839) I removed 

 some of these branches, which presented the following appear- 

 ances. The lips of the wound both above and below presented 

 a hardened exudation, which on being cut into was softer than 

 the surrounding tissues. This exudation was most abundant on 

 the upper lip of the wound. On removing the bark from 

 around the edges of the denuded surface a portion of the ex- 

 uded matter came away with the bark, whilst another portion 

 was left in connection with a layer of alburnum that had been 

 formed subsequently to the removal of the bark of the trees. 

 The section of the bark on the upper edges of the wound pre- 

 sented the same appearances, but the layer of alburnum was 

 thicker. On examining the exuded matter by the microscope 

 the external portions consisted of cellular tissue, but it was 

 distinctly fibrous where it united with the wood of the liber 

 and the alburnum. From these experiments it will be seen 

 that woody tissue as it existed in the exuded matter from the 

 lower edge of the cut, and in the alburnum under the bark at 

 the same point, must have been formed independent of the 

 descent of any fibrous matter between the bark and alburnum 

 from the leaves on the tree above the wounded part. 



The last occurrence which I shall mention in the organiza- 

 tion of vegetables, which appears to offer an argument against 



