450 TI;ANSACT10NS and PUOCEEDINGS of TIIK [Sess. i.xvm, 



that could be desired, though in other parts of the country 



this week was an exceedingly wet one. Although the list 



of rare plants found is not a very long one, still some of 



them are of great botanical interest, and well repaid the 



Members for their visit. The only rare plant reported to 



exist in this neighbourhood, but unfortunately not found 



by any member of the party, is Carcx hmnniwjhauseniana. 



On the other hand, a rare plant 'was discovered in the 



district, not hitherto reported upon. 



Note. — With regard to Centiincidus niiniinus fouiiil by ^[r. Boyd, it 

 is interesting- to note that, according to Dr. Boswell Syine, the plant has 

 never previously been found so far north in Scotland. 



Notes on the Origin of Lenticels, with Special 



EeFERENCE to TH08E OCCURRING IN EOOTS. By J. A. 



Terras, B.Sc. (With Illustration.) 



(Read 14tli April 1904.) 



That the initiation of those secondary meristematic divi- 

 sions which give rise to cortical phellogen is intimately 

 connected with, and probably dependent on, the mechanical 

 stresses set up by secondary growth in thickness, is at least 

 indicated by the constant association of the two cambial 

 rings, the formation of bundle cambium always preceding 

 that of phellogen. If this be granted, it is natural to 

 suppose that the form and structure of the cells resulting 

 from at least the earlier divisions of the phellogenetic 

 initials must to a certain extent depend on similar stresses ; 

 while in the case of later divisions, the form primarily 

 impressed on the initial cells will be retained under the 

 influence of inheritance long after the casual stresses have 

 been removed. That such a fixation of characters impressed 

 on meristematic cells by external and temporary causes 

 is common in tissues, is sufficiently indicated by the 

 phenomena occurring in the case of scar formation where 

 injury to a dividing meristematic cell causes it to form 

 daughter cells differing in character from those originating 

 from similar but uninjured parents. The difference so 

 produced may persist throughout life, or at anyrate long 

 after the disappearance of the exciting cause and even 

 of the cells originally injured. 



