LIVERWORTS 141 



with a strong alkali before examining them. I use 

 a seven-per-cent. solution of liquor potasses for this 

 purpose, though a small piece of ordinary washing 

 soda dissolved in water forms a very good substi- 

 tute. The best way to proceed is to place a branch 

 of the plant, in a few drops of the solution, on one 

 of the ordinary glass slips used for mounting micro- 

 scopical slides, to cover this with a cover-glass 

 (also employed in mounting), and, by means of a 

 pair of forceps, to hold the glass over the flame of 

 a spirit-lamp, until the liquid boils ; the specimen 

 should then be well washed by boiling it in water, 

 and it will be found that all the details of cell- 

 structure can be plainly seen in the microscope. 



There are two points in particular with regard 

 to the structure of the leaves that cannot fail to 

 attract the attention of the student. In the first 

 place he will notice that the leaf-cells of many 

 species are much larger than those of the majority 

 of moss leaves, and, moreover, that the cell- walls 

 are, as a rule, thinner (see Plate X. fig. 37). 

 In a few of the mosses, noticeably in the Thyme 

 Thread-moss (Mnium) family, we meet with simi- 

 larly large cells, and in these plants may in 

 consequence notice that the leaves are decidedly 

 filmy in appearance. In many of the liverwort 

 leaves too, when examined with a high-power lens, 

 there may be seen small enlargements of the cell- 

 walls generally somewhat triangular in shape 

 at the angles of the cells, looking as though they 



