COLLECTION, PRESERVATION, AND EXAMINATION. 109 



Filamentous and fruticulose species may be readily sepa- 

 rated from the surfaces on which they grow at their point 

 of adhesion ; they may then be dried by exposure to the 

 air or sun, and packed in small boxes, such as pill-boxes ; 

 or they may be steeped in water, subsequently dried between 

 towels, and then subjected to pressure between folds of bi- 

 bulous paper, as is done in the preparation of herbarium 

 specimens of phanerogamous plants. The latter mode is 

 the most elegant ; by it the plant may be cleansed, its seg- 

 ments tastefully displayed, and so flattened by pressure as 

 to admit of its being fastened by gum or glue to paper or 

 cardboard. This mode is however only suitable for the 

 species of certain genera, such as Usnea, Cornicularia, 

 jRamalina, Physcia, Cetraria, Collema, and some Parmelias. 

 To separate some foliaceous species from their base of sup- 

 port the assistance of an old flat knife or similar instrument 

 is necessary. Steeping in water is in some cases attended with 

 this disadvantage, that it alters the characters of the thallus 

 or apothecia ; the red colour of the apothecia of certain Cla- 

 donias is by this means changed to a dull brown. Some 

 species, such as the Cladonias and Calicia, may be collected 

 in clusters, like tufts of moss, with portions of the soil or 

 decayed wood on which they usually grow ; they may then 



