174 The Rothamsted Grass Experiments. 



dry substance there was (excepting lime) an abnormally high 

 percentage of the mineral constituents supplied, there was 

 an abnormally low percentage of those not supplied, again 

 indicating that the point of exhaustion of available supply 

 was reached. With this evidence of exhaustion of mineral 

 matter, there was an abnormally high percentage of nitrogen 

 in the dry substance of the produce of both plots, but 

 especially in that by the ammonia-salts alone. 



With this chemical evidence of repletion of nitrogenous, 

 and deficiency of mineral supply, the botanical character of 

 the herbage was equally significant. On both plots it became 

 more and more gramineous, particularly with the superphos- 

 phate, where the number of species also declined more. On 

 both plots Festuca ovina became by far the most prominent 

 grass, constantly increasing, and in 1877 it made up more 

 than half the total crop in each case. Agrostis vulgaris came 

 next in abundance, and in 1877 the two grasses, Festuca 

 ovina and Agrostis vulgaris, made up nearly 83 per cent, of 

 the total produce grown by ammonia-salts alone, and within 

 a fraction of 80 per cent, of that by ammonia-salts and super- 

 phosphate. On the plot with ammonia-salts alone, three other 

 grasses, Anthoxanthum, Holcus, and Dactylis, together con- 

 tributed about 10 per cent, more, and no other single grass as 

 much as a quarter of 1 per cent. On the other plot (46), Anthox- 

 anthum, Alopecurus, Holcus, Avena elatior, Poa pratensis, 

 and Dactylis, together contributed an additional 14 per cent., 

 and no other grass more than a small fraction of 1 per cent. 



Not only did the herbage, then, consist mainly of two 

 grasses, but the one which took the lead, Festuca ovina, is the 

 prevalent plant on poor common lands ; and on both these 

 plots both grasses showed very inferior characters of develop- 

 ment. They consisted chiefly of very dark green leafy 

 herbage, growing in patches or tufts, with very little tendency 

 to produce stem and seed, and, particularly in dry seasons, 

 dying at the bottom, without properly ripening, and always 

 yielding a soft, woolly, and very inferior hay. 



