Fig. 44. Section of Physcia parietina.
a. Cortical stratum. b. Gonidic stratum. c. Medullary stratum.
But in addition to this microscopical examination, it is also requisite to observe the different chemical reactions produced on the asci or the hymeneal gelatine with iodine (I), which will tinge these either bluish or reddish wine-coloured, or else leave them uncoloured. Similarly the thallus, including both the cortical layer and the medulla, may be tested with hydrate of potash (K), and hypochlorite of lime (C), the latter being applied either by itself or added to K when wet. In some cases no reaction will be produced by these either upon the cortical stratum or the medulla; in others they will be tinged yellowish or reddish. The formulæ for the preparation of these reagents are: for iodine, iodine, gr. j; iodide of potash, gr. iij, distilled water, 1/2 oz.; for hydrate of potash, equal weights of caustic potash and water; for hydrochlorite of lime, chloride of lime and water of any strength. After correctly ascertaining the specific name of the specimens collected, this is to be written on the slips of paper to which they are affixed, above the locality and date, and the best of them, including all varieties and forms, selected for subsequent mounting in the herbarium. This may be effected either in the same way as the mounting of phanerogamic plants, or by affixing the specimens to pieces of millboard covered with white paper, and arranging them according to the order of the genera and species in the system of classification which may be adopted. For facility of reference the latter is undoubtedly the preferable method; and if the cards are disposed in a cabinet with shallow drawers, they will not, so far at least as our British species are concerned, be found to occupy too much space.
XIV.
SEAWEEDS.
By W. H. Grattann.
In some articles published in 'Science-Gossip' a few years ago, I gave some directions for collecting and preserving Marine Algæ, or seaweeds, and although, I think, it will be difficult to simplify those directions, or even to add much that would be really serviceable to young beginners in this delightful pursuit, it is my intention, in going over the ground once more, to be as explicit as I possibly can; and here, on the threshold of the subject, I have a few words to say to one or two occasional contributors to that journal, who, in calling attention to the beauty of marine vegetation, and urging young persons to collect and preserve Algæ, have advised them to ignore books on the subject, and go to the shore, use their own eyes, and collect for themselves, &c. I am sorry very greatly to differ from such advice. Collecting in this way may be amusing enough to those who care not for science, but when it leads to parcels of seaweeds, picked up at random, being sent to botanists with a request that the names of such plants should be sent to the writer, it is the reverse of pleasure to the scientific botanist, for it gives him infinite trouble, and enables him to convey but very imperfect information to his applicant. The editor of that journal has often been thus appealed to, and packages of decayed rubbish have frequently been sent to me for examination, containing species or rather fragments of plants, which, for the most part, were utterly worthless and defied identification.
Almost all collectors commence by mounting plants which a little experience proves to be really what the old poet termed "alga projecta vilior"; but as seaweed-gathering, like everything else, requires practice, beginners must not be disappointed because they do not find rarities or fine specimens whenever and wherever they may seek for them.