EXPERIMENTS ON THE MIXED HERBAGE OP PERMANENT MEADOW. 391 
If such be the difficulty and the intricacy of the subject when the growth of a crop 
consisting of a single species only is concerned, how much more difficult and intricate 
must it be when we have to deal with the relations of the various climatal conditions 
to the development of a great variety of species growing together, as in the case of the 
mixed herbage, and numbering, as they do, under 20, or 50 or more, according to the 
varied manorial conditions provided ? 
Still, it will be of interest to show the fluctuations of produce from season to season, 
side by side with those in the characters of the seasons themselves, so far as such 
records as we have at command bearing upon the subject enable us to do so. It would, 
however, occupy far too much space to attempt to point out the connexion between 
the amount of produce and the climatal conditions of each individual season. It must 
suffice in this place to draw attention to the actual and the comparative characters of 
season under which some of the largest, and some of the smallest, amounts of produce 
have been grown. In Part II., relating to the Botanical Ptesults, the connexion 
between climatal conditions and growth will be further brought to view, in dis¬ 
cussing the characters of the seasons and the amounts and the characters of the 
growth, in the four years in which the botanical analysis of the mixed produce was 
undertaken. 
Throughout the whole period of the experiments on mixed herbage, and for some 
years prior to their commencement, the rainfall has been registered at Rothamsted. 
At first the temperature also was observed, but owing to the difficulty of securing the 
completeness of the record throughout the year, the observations were abandoned. 
We are obliged to fall back, therefore, on the published records of the observations at 
Greenwich Observatory; which, though obviously inapplicable for the discussion of the 
subject in much detail, nevertheless sufficiently clearly indicate, for our present limited 
purpose, the distinctive and comparative characters of the different seasons, or parts of 
seasons, so far as temperature is concerned. AVith regard to light, there are not want¬ 
ing so-called actinometric observations of various kinds ; and there have also been of 
late years diurnal records of the number of hours of sunshine. There is, too, reason to 
hope that methods of systematic observation and' record will before long be perfected 
and simplified ; and that, at no very distant future, data relating to the quantity and 
quality of the sunlight at different seasons of the year, or in different years, may be 
available as another element in the study of the connexion between meteorological 
influences and vegetation. In the meantime, comparative temperature is the most 
reliable basis we possess for any deductions as to the comparative amounts of effective 
sunlight, as between one and the same period of different years ; but it is obviously less 
directly applicable for the purpose of drawing conclusions as between different periods 
of the same season. 
In Appendix-Tables III. to IX. (pp. 409 to 415), are given, for each year of the first 
20, and also for each of the three subsequent years— 
