242 TRANSACTIONS OF THE [Sess. lxxviii. 



close relationships of certain sections of mosses, such as, 

 more especially, -that containing the genus Campy lopus, 

 as prevalent there, if not more so, than on our western 

 shores. In the " Annals " I have indicated three of these 

 identities. Under the assurance that such a correspond- 

 ence would continue, I expressed a wish to have species from 

 Nova Scotia or from any of the larger islands in the gulf 

 of the St. Lawrence. With one exception, I failed to obtain 

 any in a satisfactory condition. Accordingly it is possible 

 that one of the species described in this paper may have 

 been represented already by some American botanist hitherto 

 unknown to me. In such circumstances I think it due to 

 myself to give the present explanation. 



By way of introduction to this paper I may be allowed 

 to describe certain large cells which, within the last ten 

 years, have played a more important part than formerly 

 in the discrimination of species : — 



First. — Large oblong cells, generally, but not always, 

 with thickish walls, either pale or becoming more or less 

 red or brown and then opaque, situated at the base of the 

 leaf either next the margin— the usual situation of the 

 auricles, — or next the nerve, situated almost always in the 

 centre of the leaf. 



Second. — Elongato-hexagonal cells with thin walls, in 

 double layers — in other words, one layer of cells on the 

 anterior surface, the other just behind the first. This 

 question of the double layer is difficult of proof. 



I have succeeded in convincing myself of this disposition 

 of these cells in three instances where a thin cross-section 

 of the lower part of the leaf was made ; but very generally 

 a view of the entire leaf under the microscope is sufficient, 

 if such a cell is viewed at different angles, when the sides 

 will be seen to come closer or recede from one another, more 

 especially as the walls of such cells are almost always 

 parallel. The position of such groups of cells varies as in 

 the others — viz., at the alar or outer margin of the leaf or 

 at the middle base, i.e. with one side of the group in contact 

 with the nerve. 



Third. — Another cell plays nearly as important a part 

 as the others, although it is seldom or never seen quite 

 at the base of a leaf, viz. the fusiform, either hyaline or 



