R. G. Stapledon and T. J. Jenkin 39 



of secondary stabilisation and thus to give to a number of plants which 

 are probably only secondary indigenous the semblance of primary 

 species on such habitats {e.g. Lolium perenne, Poa spp., Cynosurus 

 cristatus, and Dactylis glomerata, which, if truly primary, are probably 

 only so as distributed plants). 



From these considerations it follows— since the more valuable plants 

 are usually secondary species and occur under conditions of delayed 

 stabilisation — that reasonably heavy stocking favours the development 

 of desirable pastures. 



Provided therefore that lime and phosphatic manures are adequately 

 apphed to compensate for the removal of these ingredients from the 

 soil, our sheep walks and the majority of our grasslands could be 

 enormously benefited by carrying a greater head of stock^. 



(6) A comparison of all the heath fescue types above 600', including 

 permanent grassland (over 20 years down) on land derived from heath, 

 illustrates very well the progressive stages in the competitive interaction 

 between primary and secondary species towards the end stages of grass- 

 land stabilisation^. They are as follows : 



At 20-30 years (permanent grassland above 600', p. 32). 



Under the influence of periodic manuring and comparatively heavy 

 grazing with cattle and sheep the secondary species {e.g. Cynosurus 

 cristatus, Trifolium repeats, Plantago lanceolata, etc.) are still abundantly 

 represented ; the primary species {e.g. Agrostis vulgaris, Festuca ovina, 

 and the heath herbs) are, however, beginning to take a prominent place 

 in the herbage. 



At 50-100 years (disturbed heath fescue pasture, p. 30). 



Under the influence of a discontinuance of manuring and of grazing 

 chiefly with sheep, the primary species have gained considerably but 

 do not yet stand in their normal relation to each other ; the secondary 

 species are much reduced. 



At over 100 years (undisturbed heath fescue pasture, p. 28). 



The influence of the original disturbance and of manuring is now 

 finally lost; the grazing is generally by sheep only, the nett result 

 being that the primary species have completely suppressed the secondary 

 species. 



^ A just balance between the potentialities of the herbage under the influence of 

 manures and a gradual increase in the stocking, and the limits set to the number of stock 

 carried due to pathological influences of over-crowding, is all too seldom the ideal of 

 graziers. 



2 Stabilisation in so far as the fescue types of grassland are concerned. We are not 

 here concerned to decide if the mountain fescue is an ecologically stable type. 



