142 VEGETATION OF THE PEAK DISTRICT [CH. 



Rubus Chamaemorus Melampj-rum pratense 



Emi>etrum nigrum Galium saxatile 



Erica cinerea Anthoxanthum odoratum 



Calluna vulgaris Agrostis tenuis 



+Azalea procumbens Deschampsia flexuosa 



Vaccinium uliginosum Festuca ovina 



V. M\Ttillus Luzula sylvatica 



V. Vitis-idaea L. campestris 



Are the Plants of the Cliffs and Screes Lithophytes ? 



The precipitous faces of the cliffs are tenanted by many- 

 species of Algae, lichens, liverworts, and mosses : and some of 

 these may be regarded as " lithophytes." Many of the plants, 

 however, even the lower cryptogams, are not rooted on the bare 

 rock itself, but in the loose soil which accumulates, to a slight 

 extent, on the surface of the slight irregularities of the face of 

 the rock, even when this is nearly vertical. 



Warming (1909 : 238 and 240) uses the term " lithophytes " 

 in a double sense. Section VIII of Warming's treatise is 

 headed '• lithophytes" ; and these are subdivided into (1) "litho- 

 phytes " and (2) " chasmophytes." Warming states that this 

 subdivision is in accordance Avith the suggestion made by 

 Schimper (1903 — 4: 178) who wrote: — "The vegetation on 

 the surface of rocks or stones may be termed that of lithophytes. 

 Crevices in rocks, in which more finely grained components 

 and more water accumulate than on the surface, produce a 

 somewhat more copious vegetation, that of chasmophytes." 

 Warming (1909 : 240) also cites Ottli who defines as rock- 

 plants or petrophytes " all those plants, growing on sides of 

 rocks or blocks of detached stone, which are able, as the fii'st 

 of their kind, to colonize the rock permanently, and which 

 display in distribution or structure a more or less pronounced 

 dependence upon rock as a substratum. Within this definition 

 are included both lithophytes and chasmophytes." Ottli {loc. 

 cit.) maintains that " it is not a natural scheme to co-ordinate 

 both lithophytes and chasmophytes ; and he suggests the 

 following scheme : — 



