R. G. Stapledon and T. J. Jenkin 61 



the commercial Trifolium repens (white or Dutch clover) produces a 

 lasting plant, on many types phosphatic manures being all that is neces- 

 sary to hasten the appearance of the indigenous plant. 



(6) The commercial seed may produce a great bulk of the required 

 plant in the early years of a ley (far more than the indigenous species 

 would attain to naturally at any time). It is only after some years 

 that the plant attains to its normal development, which suggests that 

 the final plant is the indigenous counterpart of the sown species. 

 The behaviour of Lolium ferenne sown on good soils is an excellent 

 example. 



Under these circumstances good seedings of the commercial seed 

 is economically justified especially if hay is required in the early years 

 of the ley, 



(c) The commercial seed may hasten the appearance of the desired 

 plant and cause it to bulk somewhat more largely in the early years 

 of a ley than it otherwise would; but there is always some risk 

 of the sown plant interfering with the development of the definitely 

 lasting indigenous species. Good examples are Poa trivialis, and 

 Cynosurus cristatus; ultra local knowledge would often suggest ex- 

 cluding the former from a mixture; while the amount of seed of 

 either that might be advantageously used requires further local 

 investigation. 



(8) The desirability or otherwise of sowing the commercial seed 

 of locally exotic species, or of but shghtly secondary species, is easily 

 decided. The commercial seeds lead to good results or they do not. 

 If the commercial seed produces plants that are found to succeed it 

 is however nearly always necessary to sow Kberally ; this is particularly 

 true of Dactylis glomerata, Festuca elatior, Cichorium Intyhus, Phleum 

 pratense, and Arrhenatherum avenaceum. 



(9) It is difficult to account for the spontaneous appearance of 

 primary and secondary species (and of some locally exotic species, 

 e.g. Holcus lanatus, Bromus mollis et spp. and Phleum pratense) on 

 land long under the rotation when put down to grass ; especially when 

 more or less isolated from natural or semi-natural grasslands. The 

 available evidence, however, suggests that 



(a) Many species remain on the land as arable weeds, e.g. on the 

 soils that suit them, Poa trivialis, Agrostis vulgaris, Festuca rubra, and 

 Ranunculus repens. 



(b) The seeds of many species are probably introduced by the wind 

 e.g. Holcus lanatus, Anthoxanthum odoratum. 



