To Joseph Henry Gilbert   3 June [1869]¹

The year is established by the position of this letter in a chronological set in a bound volume of Gilbert’s correspondence at the Rothamsted Experimental Station.

Gilbert had probably invited CD to visit the grass experiments at Rothamsted; in a letter dated 5 June 1881 (Calendar no. 13196), Gilbert invited CD again: It is just at this season that our “Grass-Experiments” are at their best for inspection; and although the agricultural result is not very promising, I think the differences among the 20 plots, now in the 26^th season of experiment, are perhaps as striking as ever, as illustrating the vast influence of external conditions on the character and results of the struggle between the numerous components of an established mixed herbage. CD discussed the results of growing a single species of grass or many different genera of grasses in Origin, pp. 113–14.