92 



TABLE II. LiCHENES. The members of the present group are 

 CASE compound organisms, in other words, a lichen consists of two 

 L, distinct elements, a fungus and ar; alga, living together in what 

 has been termed commensalism. 



Diagrams illustrating the structure of lichens are exhibited 

 on the Gallery (Room No. 9)*; the portions coloured green 

 represent the algal component, the colourless portion the fungus, 

 bearing the fruit. 



Lichens grow on rocks, trunks of trees, and on the ground. 



No. 240. Reindeer Moss (Cladonia rmigiferina, 

 Hoff.), common on our hills and heaths in lowland, sub-alpine, 

 and alpine districts. It has a wide geographical range. In 

 Lapland it covers barren plains, and is the food of the reindeer 

 during winter, and it has even, when powdered, been mixed 

 with flour and made into bread in times of scarcity. 



Observe sample of Alectorla jubata, Ach., known as Tree 

 or Rock Hair or Horse-tail Lichen. It occurs on forest 

 trees, and has a wide geographical range. In the Highlands 

 of Scotland it is used for stuffing mattresses. 



The lower part of the Table Case is devoted to specimens 

 of Orchil, Cudbear and Litmus, dye substances obtained 

 from Roccella tinctoria, DC, R. fuciformis, Ach., and R. 

 Montagnei, Bel., all widely distributed species. Specimens 

 are shown from various countries, together with dyes pre- 

 pared from them. In commerce they are generally known 

 as Orchella Weeds. At one time the importation of these 

 dye lichens represented a very large sum, of late years, 

 however, they have been declining in consequence of the 

 introduction of the anilin or coal-tar dyes. Litmus is 

 valuable as a test for the presence of acids wdiich change its 

 purple colour to red. 

 TABLE In the upper part of this Case observe the following :^ — 

 CASE Specimens of woollen materials dyed in Scotland with ParmeUa 

 N. saxatilis, L., one of the lichens popularly known as Crottal. 

 Sample of ParmeHa perlatay Ach., a species common in low- 

 land and sub-alpine districts, and at one time imported to a 

 considerable extent into London from the Canary Islands, 

 under the name of Canary Rock Moss, for dyeing. 



TABLE No. 241. Iceland Moss (tor«n« zvf/awc?/m, Ach.). It 



CASE has a wide range in arctic and antarctic climates, and grows 



M. abundantly on most of our higher northern mountains. It 



contains a large amount of starch, and is consequently used as 



