LICHENES. 269 



88. L. TARTAREA. On rocks, not uncommon. 



89. L. viTELLiNA. On stone walls, near the base, common. 

 L. citrina, Fl. Berw. ii. p. 8.5. 



90. Pertusaria communis. On trunks of trees. Var. /3. leio- 

 placa: on the Birch. Fl. Berw. ii. p. 103. 



91. Variolaria conspurcata. D. On sandstone rocks at 

 Iludshead. 



92. V. DiscoiDEA. On trunks of trees, occasionally. 



93. V. FAGiNEA. On trees, especially of Beech and Ash, near 

 the base of the trunk, abundant. 



94. Spiloma gregarium, var. a, cinnabarinum. On the bark 

 of trees, not common. 



95. Lepraria flava. On the rugged bark of trees near the 

 base of the trunk. 



96. L. ALBA. On Hypna and Lichens in shaded situations. 



97. L. latebrardm. On rocks in caverns; and on stumps of 

 old hedges, common. See Fl. Berw. ii. p. 103. — This ambiguous 

 production is omitted in Hooker's English Flora. 



It is a favourite speculation with popular wiiters, and with many 

 botanists, that Nature begins her work of clothing the naked surface 

 of new soils, and of rocks especially, with crust-like and leprous 

 Lichens. These, by their decomposition, and by some solvent action 

 on the rock, are asserted to prepare a little soil wherein mosses may 

 germinate and root ; and thenceforward there is an easy way, in time, 

 made for the appearance of the grasses, herbs, and trees. "The growth 

 of vegetation," says Professor Schouw, " upon naked cliffs commenced 

 with lichens and mosses, which produced a little mould and accumula- 

 tions of water, in which the seeds of other plants could germinate ; and 

 plants of greater dimensions, bushes and trees, gradually made their 

 appearance." The Earth, Plants, and Man, p. 24. — The picture is, 

 I believe, an ideal one, — perhaps an offshoot of that theory of deve- 

 lopment which apparently has charms to seduce us to its entertain- 

 ment, in spite of all observation and fact to the contrary. There is 

 no proof of such a succession of vegetation in nature as that above 

 indicated ; and all I have seen is opposed to the existence of it. In 

 these days of road- and rail-making there are many places where it 

 might be traced. Now, what I observe is this : — If the exposed 

 surface of the rock is smooth and damp, confervoid growths, which 

 are but the rudiments of mosses, cover the wall about the base where 

 the air is stagnant and loaded with moisture ; and mosses and pha- 

 nogamous plants get a precarious footing higher up. But if less 

 smooth, and the surface is exposed to a fresher air, the first plants 

 that appear are the Blue-Bell, two or three grasses, the Craw-toes, 

 several mosses of the genera Tortula and Funaria, a tuft of Dande- 

 lion, a Thistle, or a Docken. These will occupy the surface — die and 

 be renewed — for years before a puny Lichen appears ; and when the 

 tribe comes at length with a few scaly representatives, the contribution 



