Fig. 37. Ceratodon purpureus.
a. Male plant. 1. Leaf and its areolation. 2. Capsule. 3. Calyptra 4. Two teeth of the peristome.
2. In mounting specimens for the herbarium we must be guided by the limits which we have fixed on for the extent of the same; and I may first describe the method adopted for my own collection. Every species has a separate leaf of cartridge-paper measuring 14-1/2 × 10-1/2 inches, and on this the specimens are fixed, each mounted by a little gum on a piece of toned paper; thus 4 or 6 to 12 specimens, according to size, are attached to each leaf,—varieties have one or more additional leaves; and to each is also fixed a triangular envelope, inclosing loose capsules and leaves for ready transfer to the microscope, and also a label indicating the name, habitat, and date of collection. A pink cover for each genus includes the species, and a stout millboard cover embraces the genera of each family, with the name of which it is labelled outside, the whole shutting up in a cabinet.
Another form is that seen in Rabenhorst's Bryotheca Europæa, quarto volumes of 50 specimens, one occupying each leaf, and so arranged that the specimens do not come opposite to each other. Others again use loose sheets of note-paper, within each of which a single specimen is mounted; but this, from their size, is very cumbersome. Or we may take a single well-chosen typical specimen and arrange many species on a page, as is seen in the beautiful volume of Gardiner's 'British Mosses' or McIvor's 'Hepaticæ Britannicæ.' Whatever plan we adopt, our specimens, once well dried and kept in a dry place, are unchangeable, and are always looked upon with pleasure, each recalling some pleasing associations, or perchance reminding us of some long-lost friend, in companionship with whom they were collected or studied. A stock of duplicates must also be reserved, from which to supply our friends, or exchange with other collectors for desiderata in our own series: these may be kept in square cases of various sizes, cut so as to allow the edges of the top and sides to wrap over the other half folded down on the specimens.
The Hepaticæ of the family Jungermanniaceæ are treated precisely as mosses, the capsules, however, show but little diversity, and will not require separate preservation; but the elaters, or spiral threads accompanying the seeds, are elegant microscopic objects. The Marchantiaceæ must be pressed when fresh, as they do not revive with the same facility as other species, owing to their succulent nature and numerous layers of cells.
Classification.—On this I have fully treated elsewhere ("The Moss World," 'Popular Science Review,' Oct., 1871), and it may suffice here simply to indicate the families of British mosses and their mode of arrangement. The cell-texture of the leaf takes an important place in the characters, and in accordance with this principle the Cleistocarpous or Phascoid group is broken up and distributed in various families. We have two orders; one indeed, comprising only the genus Andreæa, is distinguished by the capsule splitting into four valves united at apex; the other, including the bulk of the species, has in most cases a lid, which separates transversely, and usually discloses a peristome of tooth-like processes. The structure of these teeth again enables us to form three divisions. In the first they consist of a mass of confluent cells; in the second, of tongue-shaped processes, composed of agglutinated filaments; and in the third, of a double layer of cells, transversely articulated to each other, the outer layer composed of two rows of firm coloured cells, the inner of a single series of vesicular hyaline cells, on which the hygroscopic quality of the tooth depends.
Sub-Class SPHAGNINÆ.
Bog Mosses.
Fam. 1.—Sphagnaceæ.
Sub-Class BRYINÆ.
Frondose Mosses.
Order 1.—Schistocarpi.
Fam. 1.—Andreæaceæ.
Order 2.—Stegocarpi.
Div. 1.—Elasmodontes.
Fam. 2. Georgiaceæ.
Div. 2.—Nematodontes.
Fam. 3.—Buxbaumiaceæ.
Fam. 4.—Polytrichaceæ.
Div. 3.—Arthrodontes.
Subdiv. 1.—Acrocarpici.
*Distichophylla.
Fam. 5. Schistostegaceæ. | Fam. 6. Fissidentaceæ.
**Polystichophylla.
Fam. 7. Dicranaceæ. | Fam. 12. Splachnaceæ.
" 8. Leucobryaceæ. | " 13. Funariaceæ.
" 9. Trichostomaceæ. | " 14. Bryaceæ.
" 10. Grimmiaceæ. | " 15. Mniaceæ.
" 11. Orthotrichaceæ. | " 16. Bartramiaceæ.
Subdiv. 2.—Pleurocarpici.
Fam. 17. Hookeriaceæ. | Fam. 20. Leskeaceæ.
" 18. Fontinalaceæ. | " 21. Hypnaceæ.
" 19. Neckeraceæ. |
Sub-Class HEPATICINÆ.
Liver Mosses.
Fam. 1. Jungermanniaceæ. | Fam. 3. Anthocerotaceæ.
" 2. Marchantiaceæ. | " 4. Ricciaceæ.
Among species which may be generally met with by beginners on the look-out for mosses, we may enumerate the following:
On Walls.—Tortula muralis and revoluta, Bryum capillare and cæspiticium, Grimmia pulvinata, Weisia cirrhata.
In Clay Fields.—Phascum acaulon, Pottia truncatula and Starkeana.