PLANT INDICATORS. 



55 



favour the growth of certain characteristic plants of the sub- 

 climax stage, and of how those conditions affect tree-growth. 

 In its present state our knowledge is crude, with many blanks, 

 and experiments, observations, and records are greatly needed. 

 In making observations one must bear in mind the influence 

 that man and other extraneous factors may have on the flora. 

 These may have created changes before the time of study, as 

 where a destroyed coniferous wood has been replaced by Aira 

 flexuosa, or a burned area of spruce by Epilobuim — neither of 

 which will remain for many years. Or, on the other hand, man 

 may so change a site by drainage that Scirpus or Eriophorum 

 bog may be replaced by Molinia, N'ardus, or Calli/fia, and 

 ultimately by tree-growth. 



The following is a general table showing briefly the conditions 

 under which various plants used as indicators may be found, 

 and also the species of tree which are usually planted under 

 such conditions : — 



Name of Plant 



Calliina vulgaris, 

 Salisb. 



Erica Tetralix, 

 Linn. 



Erica cinerea, Linn. 



J'accinitim Alyrtil- 

 lus, Linn. 



Vacciniinn Vitis- 

 fdaea, Linn. 



Airaflexuosa, Linn. 



Common Name 

 of Plant 



Ling or lieather. 



Cross - leaved 

 heath. 



Bell heather. 



Bilberry, 



blaeberry, 



whortleberry. 



Cowberry, 



red whortleberry, 



cranberry 



(in Scotland). 



Wavy-hair grass. 



Indicates 



Peat, which may be deep 

 or shallow — conditions 

 indicated by the other 

 plants existing, and also 

 by the condition of 

 heather. 



Generally associated with 

 Calliina in wet peat. 

 Requires drainage. 



Drier peat in mixture 



with Calliina. 

 Drier peat, not deep ; 



occasionally appears 



with grasses in fresh 



peat. 

 Peaty soils, usually with 



Calluna and Vac. Myr- 



tillus. 



Chalk and limestone, or 

 on heath or moors on 

 gravelly soils. Acid 

 conditions. Often the 

 first plant to succeed on 

 blown-out parts or clear- 

 ances of woods. When 

 in mass it often indicates 

 dry conditions. Often 

 with Calluna. 



Tree 



Scots pine. 

 Good larch has 

 been grown on 

 soil with shal- 

 low peaty sur- 

 face. 



Scots pine after 

 drainage. Oc- 

 casionally Nor- 

 way spruce. 



Scots pine, some- 

 times larch. 



Scots pine, son.e- 

 times larch or 

 birch. 



Scots pine, some- 

 times larch or 

 birch. 



pine, 

 beech 



Larch, 

 birch, 

 as improver. 

 After scrub 

 in sheltered 

 places, Doug- 

 las fir, etc. 



