68 MEMORANDA OF PLANTS, COLLECTED 



mode of origin of the isolated tissues horizontally developing 

 upon the exposed alburnum have been shown to be incorrect. 



REFERENCE TO PLATE II. 



Fig. 1. Transverse Section of " Couche generatrice^^ re-estab- 

 lished on the exposed surface of the alburnum of a sycamore, 

 alluded to at page QQ. d. Wood-cells (prosenchym), and medul- 

 lary rays of previous year. c. This zone of comparatively thin- 

 walled tissue, with vessels, and continued rays, was formed 

 probably in the earlier part of the year in which the experiment 

 was instituted, a. This layer may be considered as an outer 

 zone of c, beneath which, and sufficiently protected from undue 

 evaporation, &c., a zone (6) has assumed the office of " Couche 

 generatrice'"' and it is here, doubtless, that future multiplication 

 of cells in a horizontal direction would obtain ; a eventually 

 forming a pseudo-derm. It will be observed that the cells, both 

 of the future woody bundles, and of the medullary rays, equally 

 share in this growth. 



Fig. 2. Pear Tree. a. a. c. Cellular formations upon the surface 

 of the denuded alburnum ; some of these are isolated, others in 

 vertical continuity with the bark. The stem upon which this 

 decortication was effected was sawn off three inches above the 

 upper edge of the annulus. 



Fig. 3. Elm. h. h. Exhibit the development of cellular tissue 

 in upward and downward directions : the cellular annulus of the 

 upper edge probably originates from the inner cortical layers, as 

 well as from the " Couche generatrice^'' a. The exposed al- 

 burnum. 



IV. — Memoranda of Plants, collected by the Coquet, in 1855. 



By D. Oliver, Jun. 



[Read, November 15th, 1855.] 



A brief visit, in the course of the past summer, to Alwinton, 

 and the neighbourhood of Rothbury and Harbottle, enabled me 

 to catalogue several species of plants, with the occurrence of which 

 in that district we were previously unacquainted. Nearly every 



