EUROPE AND NORTH AMERICA. 7 



wise the stems are sure to be broken ; quick transference to the 

 press, and a frequent change of drying paper, will usually ensure a 

 satisfactory result. 



We may point out to the tyro a few other characters by which 

 our plants are distinguished from the true mosses. If we examine 

 a single stem we find that the branches are in fascicles or clusters, 

 i. e. spring several together from one point, and at the top are 

 closely packed in a roundish head or coma ; if we look at the 

 leaves of one of these branches under the microscope, we find they 

 consist of a network of large empty cells which contain threads 

 winding spirally round on the interior of the membrane, and are 

 bounded by a dark line of narrow cells filled with chlorophyl ; the 

 capsule also is sessile on the dilated end of a naked branch. For 

 the determination of species, however, a more minute examination 

 is necessary, as besides the form of the various leaves we also 

 require a knowledge of their internal structure, as well as that of 

 the stem ; this is obtained by transverse sections of them, suffi- 

 ciently thin to allow the light to be transmitted, and these are 

 best examined in water and uncovered. 



The simplest mode of making the sections is to enclose the 

 wet stem or branches in a split vial cork and tie them tight, then 

 with a razor to make very thin slices of the whole, placing them 

 in a few drops of water on a slide, when they will immediately 

 expand and the cork may be picked out with a needle. Russow 

 recommends that the whole plant be soaked in thick mucilage and 

 allowed to dry, and then cut with a razor into water. Certain 

 reagents are also of use in the examination of cell structure, as 

 iodine and sulphuric acid, or a solution of biniodide of zinc, by the 

 action of which the Sphagnum leaf is coloured blue or reddish, 

 and all its details of structure sharply defined. Heating the leaves 

 on a slide in a little liquor sods is of value in enabling us to obtain 

 a clear view of the outline and condition of the walls of cells. 



For those who have time and the necessary skill, the various 

 parts may be mounted permanently on slides in glycerine, or other 

 fluid suitable for vegetable tissues, and they then form very useful 

 objects for comparison with any specimens which may be the 

 subject of examination.* For the herbarium, it is better to 

 separate the tufts into thin layers before submitting them to 

 * The Rev. Mr. Vize, of Forden Vicarage, Welshpool, has put up sets of the 

 British Sphagna mounted in this manner. 



