J. H. Gilbert— Points in connection wit], Vegetation. 31 



age on selected plots in the seventeenth season of the experi- 

 ments (1872). The quantities of the different plants there 

 exhibited represent the relative proportion, by weight, in 

 which each species was found in the mixed produce of the 

 different plots; and the whole illustrate* in a striking maimer 

 the domination of one plant over another, under the influence 

 of different manures, applied year alter year on the same plot. 



The general results of the experiments may be briefly sum- 

 marized as follows :— 



The mean produce of hay per acre per annum has ranged, 

 on the different plots, from about twenty-three cwt. without 

 manure to about sixty-four cwt on the plot the most heavily 



The number of species found has generally been about fifty 

 on the unmanured plots, and has been reduced to an average 

 of only twenty, and has sometimes been less, on the most 

 heavily manured plots. 



Species belonging to the order Graminem have, on the aver- 

 age, contributed about sixty-eight per cent of the weight of 

 the' mixed herbage grown without manure; about sixty-five 

 per cent of that grown by purely mineral manures (that is, 

 without nitrogen); and about ninety-four per cent of that 

 grown by the same mineral manures, with a large quantity of 

 ammonia-salts in addition. 



Species of the order Leguminosce have, on the average, con- 

 tributed about nine per cent of the produce without manure, 

 about twenty per cent of that by purely mineral manures 

 (containing potass), and less than 0-01 per cent of that by the 

 mixture of the same mineral manures and a large quantity of 

 BE&moniacal salts. 



Species belonging to various other orders have, on the aver- 

 age, contribute,! about twenty -three per cent of the produce 

 without manure; about fifteen per cent of that by purely 

 mineral manures, and only about six per cent of that by 

 the mixture of the mineral manures and a large amount of 

 ammonia-salts. 



Not only the amounts of produce, but the number ana 

 description of the species developed, have varied very greatly 

 between the extremes here quoted, according to the particular 

 character or combination of manure employed, and to the char- 

 acter f ti : kinglj illustrated by the arrange- 

 ment of the specimens in the eas v i. own er, it should 

 be borne in mind, show the composition of the herbage on the 

 selected plots in one particular season only— namely, in 18/2. 



Obviouslv, these few remarks can only very inai 

 indicate the interest of these - of the dom- 



ination of one plant over another in the mixed herbage of per- 



