534 



HUTCHINSON'S POPULAR BOTANY 



each? of these groups, for some of the foliaceous Lichens are of very hard 

 texture, and to these the term crustaceous is applied. So. too, some fruticu- 

 lose Lichens have their lobes or branches reduced to fine threads and 

 are therefore denominated filamentous. The Beard Moss ( Usnea dasypoga, 

 fig. 673) is of this kind. 



Neither Algse nor Fungi are long-lived plants, although the woody Fomes 

 among the Fungi may subsist for twenty years or so ; but no such limit can 

 be set to the life of some of the foliose Lichens. Any one who over a long 

 period of years has made observations in any particular district must have 

 noticed how certain patches of Lichens on old walls or rocks maintain their 

 position with little apparent increase of size. The combination of the two 

 elements in their structure appears to give them the power of almost per- 

 petual renewal. Berkeley expressed his belief that " Patches of such 

 Lichens as Lecidea geographica probably date from almost fabulous periods, 

 and even small patches are often of considerable age. I have myself 



watched individuals for 

 twenty-five years, which 

 are now much in the same 

 condition as they were 

 when they first attracted 

 my notice." The same 

 belief must have been in 

 Euskin's mind when he 

 penned a much-quoted 

 passage in " Modern Pain- 

 ters," for one of its sen- 

 tences runs : " The orange 

 stain upon the edge of 

 yonder western peak re- 

 flects the sunsets of a thousand years." This durability of the living Lichen 

 remains when specimens have been collected for reference by the student. 

 This fact should make the group a favourite one with collectors, though 

 it has not done so to any extent. Lichens require none of the troublesome 

 preparation demanded by most natural history specimens. Exposure to 

 the indoor atmosphere without pressing in porous paper will secure their 

 satisfactory drying with little (in many cases no) loss of the living form, 

 and even in those cases where there is shrinkage a few minutes' soaking 

 in tepid water will restore the plumpness and pliability that may be 

 necessary for purposes of study. 



It was formerly held that Lichens obtained their nourishment entirely 

 from the atmosphere, but the modern view is that the rhizoid filaments of 

 the Fungus partner draw water and mineral substances from the stratum 

 upon which it grows, and this material, useless to the Fungus, the Alga 

 can work up in the sunlit upper tissues into proteids upon which the Fungus 



FIG. 678. BROWN MOULD (Mucor mucedo). 



(a-c) Gonidia from which the plant develops, (d) Sporange. (?) The 

 same bursting to release the spores. 



