216 The Rothamsted Grass Experiments. 



ammonia-salts, where Dactylis glomerata, which was both 

 abundant and forward, suffered very much. 



The four selected seasons most strikingly illustrate the 

 intricacy and difficulty of the attempt to trace the relation 

 between the amount of growth of the mixed herbage of grass 

 land, and such meteorological conditions as are sufficiently 

 recorded. Very dissimilar climatal conditions characterised 

 the two seasons of highest productiveness, and again very 

 dissimilar ones those of lowest productiveness. The character 

 of the produce was also very different in the two cases of 

 the largest crops, and again very different in the two of the 

 smallest crops. 



Taking a comprehensive view of the four seasons, it is 

 apparent tTiat in both seasons of high productiveness the 

 period prior to that of most active above-ground growth had 

 brought the herbage into an unusual state of forwardness ; 

 when, in the one, abundance of rain, with, upon the whole, 

 low temperatures, gave great luxuriance, but comparatively 

 leafy, succulent, and immature produce ; whilst, in the other, 

 the luxuriant early growth was followed by both unusual 

 drought and unusual heat, yielding quantity by virtue of 

 high development and maturation, as distinguished from 

 succulence and immaturity. As in both the cases of high 

 productiveness the period antecedent to that of most active 

 growth had been favourable, so in both those of very defec- 

 tive growth they had been very unfavourable. The winter 

 and early spring of 1870 had not, upon the whole, been 

 deficient in rain, but the period had been extremely variable 

 as to temperature, frequently very inclement, and, upon the 

 whole, colder than usual. The herbage was, from these 

 causes, very backward at the commencement of the active 

 growing period. April, May, and June followed, with a 

 great deficiency of rain, very high day and low night 

 temperatures, yielding very stunted and prematurely ripened 

 produce. The winter and early spring of 1874 had, on the 

 contrary, been very unusually deficient in rain, whilst the 



