EXPERIMENTAL ORASB PLOTS. At a meeting of the Watford Natural History Society, an interesting paper was read by Mr Wallis on the botany of the ex perimental grass plots at Rothamsted. In the year 1856 Mr. Lvwi»B set apart about eight acre* of gra 1 * land in his p irk at Rotharosted for the pnrpose of investi gating the comparative effects of differen 1 manuring «übatances upon permanent grass ; in the first instance, probably to d - termine the b^st means of more tsing the groan amount of produce. But not only haß the general oharacter of the herbage as to vigour, oolour, date of ripeniug, &c, materially altered, but the composition ot Ihe produce is entirely changed. The por tion of land on which the experiments have been conducted in h«»*vy loam, with a re ■ clay Rubsoil of several feet in depth imme di itrly overlying 1 the chalk, and ha? prob ably been laid down with grass for some oenturies. No fresh seed haa been arti ficially sown within the hist fifty years cer teinly, nor is there any record of any having been so *m ainoe the grass was first lai' 1 down. When the experiments com menced, the character of the herbage ap peared uniform all over the plot , which wore twenty in number, of a quarter to half-an-acre each. The same kind of mn nure was "pplied, year after year, to the same space of gruund, two pieces being Mt as te-^t plots, and entirely uumanured and the results, which are fully and care fully notpd, are very extraodinary. Be sides weighing the produce obtained by the different manures as hay, and taking samples for the determination of itH chem ical composition, namely, r'ry mntber, ash, nitrogen, woody fibre, fatty mattpr, &c, &c M carefully averaged samples aro taken in each year from all the plotn, and every year from selected plots and Hibmitted to careful botanical separation, and the per centage by weight of each species in the mixed herbage determined. The general result of the experiment may be briefly summarised as follows: — The mean produce of hay per aero per an num has ranged on the different plots from about 2lcwt. without manure to about 63cwt. on the plot most heavily manured. 