HARDWICKE'S SCIENCE-GOSSIP. 



219 



lichenist has not to wait for any particular month 

 or months, as other botanists have to do, before be 

 can collect the objects of his search in a fully- 

 developed condition. Spring, summer, autumn, and 

 even winter, except when the snow conceals all 

 vegetation beneath its white mantle, are all alike to 

 bim, and in each he will find every species of lichen 

 in perfection. At the same time, he will be most 

 successful after a shower of rain or a slight frost 

 has fallen, inasmuch as, becoming swollen with the 

 moisture then imbibed, many of the minuter species, 

 which might otherwise be overlooked, are more 

 readily perceived, and the foliaceous species more 

 easily removed from the substratum to which they 

 are more or less closely affixed. 



Nothing more need be said on the collecting of 

 lichens, as a short experience will be more useful 

 thau further details. We proceed, therefore, to give 

 a few hints on their subsequent preservation. This 

 is a very easy process, presenting no difficulty 

 whatever, and occupying but little time. We 

 shall suppose that the collector has returned 

 from a successful expedition, with his vasculutn 

 or haversack well filled vfith specimens from all 

 sorts of habitats. Openmg the papers in which 

 they have been wrapped up, he will take them 

 out one by one, and place them separately upon 

 a table, over which a newspaper has previously 

 been spread. If gathered in wet weather, they 

 ought not to be left long in the papers, as in this 

 case they are very apt to become covered with 

 mould. After allowing them to remain in this 

 position till they are thoroughly dry, he may at 

 once proceed with hammer and chisel, or with 

 knife and scissors, to reduce to a suitable size such 

 of them as he could not conveniently thus manipulate 

 in the field. When this is done, they may then be 

 affixed with gum, of a rather thick consistency, to 

 slips of white paper, with the locality and date of 

 their collection written beneath. There will be no 

 difficulty felt in thus affixing saxicole, corticole, 

 and lignicole species, though where the nature of 

 the stone or wood is more absorbent, several appli- 

 cations of the gum may be necessary before they 

 properly adhere. With terricole species, however, 

 a somewhat more lengthened process is necessary, 

 owing to the brittle nature of the substratum, in 

 consequence of which, if not properly preserved, 

 they often crumble into dust in the herbarium. To 

 prevent this, M. Norman, of Trotnsoe, Norway, has 

 recently prescribed a solution of isinglass in spirits 

 of wine, which, when liquefied in a vessel plunged 

 in water of the temperature of 25°-30^ C, is 

 greedily imbibed by the earth, and becomes inspis- 

 sated into a solid gelatine at a temperature below 

 15°. This solution may be applied until the earth 

 becomes thoroughly saturated, and after it is 

 perfectly dry, the specimen will possess sufficient 

 hardness and tenacity, and may then be mounted 



like the others. So far, however, as my own ex- 

 perience goes, I have found a weak solution of gum- 

 arabic, frequently repeated, and applied to the 

 under surface and edges of the specimens, to be 

 quite as efficacious; and if after becoming thoroughly 

 dry, they be first affixed by a thicker solution to 

 slips of thin tissue-paper, they will be equally ready 

 for being mounted as above. Either of these two 

 methods may also with advantage be applied to such 

 species as grow upon decayed mosses. Slight pres- 

 sure may be applied to the thallus of fruticulose, 

 filamentose, and foliaceous species, in order that 

 they may lie better in the herbarium ; but this 

 should be done only to a very limited degree, so as 

 not to obliterate the normal appearance of the 

 branches or lobes. As the character of the under 

 surface of the thallus is frequently of great im- 

 portance, at least in foliaceous and fruticulose 

 plants, a portion of this, not Hecessarily detached, 

 should be turned over, for facility of inspection, 

 and pressed down on the paper, before the speci- 

 mens have become quite dry and rigid. In order to 

 destroy any insects that may be upon the plants 

 when gathered, or by which they may afterwards be 

 infested, Hellenists at one time were in the habit of 

 poisoning them with corrosive sublimate. Erequent 

 exposure, however, to the air in dry weather, and 

 the presence of a little camphor, will be quite 

 sufficient to prevent any mischief from this source. 

 But having thus arranged, though the arrangement 

 is but temporary, the specimens gathered, on slips 

 of white paper, the next and most important point 

 is their due examination and determination. This 

 in the present advanced state of Lichenology, is 

 unquestionably, in many cases, a task of considerable 

 difficulty, and in the short space at our disposal, it 

 would be quite impossible to give anything like an 

 adequate explanation of the mode in which this is 

 to be effected. Suffice it at present to say that 

 sections must be made of the thallus to ascertain 

 the character of its different layers, as also sections 

 of the apothecia and spermogones to ascertain the 

 nature of the spores and spermatia. Eor both 

 purposes a good microscope, with i-inch object- 

 glass, is absolutely indispensable to the student. 

 The examination of the spores, upon which, in so 

 many cases, the determination of the species chiefly 

 depends, should present little or no difficulty, at 

 least to the fungologist. It may be readily effected 

 by moistening the apothecium with water, and then, 

 with a dissecting-knife, making a thin vertical 

 section through its centre. Putting this on a glass 

 slide, or in a compressorium, in a drop of hydrate 

 of potash, and then placing it under the microscope, 

 a view will be obtained of the asci, spores, para- 

 physes, hypothecium, &c., each of which may after- 

 wards be insulated and examined more minutely in 

 detail. Take, for example, the well-known beautiful 

 yellow lichen {Phi/scia parietitia), so common every- 



l2 



