30 TUANSACTIUNS AND I'KOCEEDING.S OF THK [Sk.ss. lxv. 



in addition, several plants are found to spread. The most 

 usually seen are Cei'astium ylomeratum, C. trivicde, Sagina 

 prociLmhens, Cnictis lanceolatus, Senicio Jacobcea, Prunella 

 vidfjaris, Polygonum avicidare, P. Persicaria, Plantago major, 

 P. lanceolata, and occasionally individuals of CaiJsella Bursa- 

 pastoris, Spergula arvensis, and Galeopsis Tetrahit. These are 

 all more or less doubtfully natives, some are undoubtedly 

 introductions, and none of them have the same standing as 

 the genuine native flora. The undoubted native plants 

 which are found on these roads in no way differ from the 

 immediate surrounding flora. The third kind of road in 

 the Highlands, the carriage road, is only noticeable for the 

 increase along it of Taraxacum officinale and Cardamine 

 hirsiUa, and on the parapets and bridges faced with lime of 

 Asplenium Rida-muraria, and the moss Encalyp)ta strepto- 

 carpa. 



For the dates given of the introduction of crops, etc., 

 into the Highlands, I am indebted to Walker's " Economic 

 History of the Highlands," published in 1812 after the 

 author's death. Dr. John Walker, who was appointed to 

 the Chair of Natural History in the University of Edinburgh 

 in 1779, was a naturalist who has not received sufficient 

 recognition. An account of his contributions to the natural 

 history of Scotland would be interesting and instructive. 



The Use of the term Bakk in recent Text-books 

 OF Botany. By li. Tuknbull, B.Sc, Extra-Academical 

 Lecturer on Botany, School of Medicine, Edinburgh. 

 (Read 14th February 19M1.) 



Until 1884, botanists were unanimous in defining the 

 bark of trees as consisting ot all the tissues outside the 

 cambium zone. The popular definition is " everything out- 

 side of the wood." These two definitions are practically 

 one and the same, since the cambium is known only to the 

 vegetable anatomist. 



In 1884, an English translation of De Bary's "Com- 

 parative Anatomy" (1) uppeared, and it was found to 

 contain an entirely new definition of bark, viz. " The 

 masses of tissue cut off" by the corky layer." This is 

 given on the authority of von M(jIi1, so that bark, according 



