14 On Bog Mosses. 



The spherules are now ground down on a flat cast-iron plate, 

 with fine emery, to the level of the block, and the whole surface 

 together is smoothed with the finest emery, taking care not to go 

 much below the surface. This is then polished with fine crocus, 

 on a bed of beeswax hardened with resin, and made to revolve as 

 in the lathe in order to expedite the process. 



All the lenses (which if the manipulation has been good are 

 perfectly flat to the edges) are now picked out while hot with a 

 pointed brass wire and dropped into alcohol to dissolve ofi* the 

 adhering lac. 



It is more easy to make one hundred lenses this way than to 

 grind and polish a single one of one-fiftieth radius by the usual 

 method. Of course their dimensions and accuracy are a matter of 

 chance, but for the purpose specified I found that they acted 

 perfectly if properly selected. 



YS[.—On Bog Mosses. By E. Bkaithwaite, M.D., F.L.S. 

 Plate XXII. 



Group C. Bigida. — Plants densely ramulose, forming compact 

 cushion-like tufts. Branch leaves erecto-patent, oblong, concave, 

 very narrowly bordered, the apex obtuse, truncate, and toothed, the 

 margin involute for great part of its extent. 



8. Sphagnum Angstromii 0. Hartm. 

 Skand. F]. 7th ed. p. 399 (1858). 

 Plate. 

 Syn.— Lindb. Torf. No. 10 (1862). Russow Torf. p. 79 (1865). Sph. cymhifolium 



o 

 /3 c(n~di folium. Hartm. Skand. Fl. 3rd to 6th ed. (p.p.). '9p/i. insulomm Angstrom 

 M. S.— Schimper Synop. p. 683 (1860). Milde Bryol. Siles. p. 390 (1S69). 



Bioicous, in large soft dense pale green tufts, light ferruginous 

 below. Stem simple, or sometimes dichotomous, whitish, with 

 three layers of thin-walled cortical cells, free from fibres or i^ores. 



EXPLANATION OF PLATE XXH. 



o 

 Sphagnum Angstromii. 



a. — Female plant, a d. — Male plant. 



1 . — Part of stem with a branch fascicle. 



2. — Catkin of male flowers. 



3. — Fruit and perichsetium. 4. — Bract from same. 



4 p. — Point of an inner bract. 



5.— Stem leaves. 5 a a. — Areolation of apex of same. 



6. — Leaf from middle of a divergent branch. 



6 p. — Point. 6 a a. — Areolation of same. 



6 c. — Single cell from same x 200. 



6 X. — Transverse section of same. 7. — Basal intermediate leaves 8. — Leaf from 



a pendent branch. 9 x, — Transverse section of stem. 10. — Part of a 



branch denuded of leaves. 



