1296 
MESSRS. J. B. LAWES, J. H. GILBERT, AND M. T. MASTERS, 
Number of species. —According to the tables, the total number of species found in 
the samples from plot 3 was, in the four separation-years respectively—50, 43, 49, and 
52; and in those from plot 12—44, 50, 50, and 51. These it is to be understood 
are the numbers of species found in the samples; but reference to Table XXXVI., 
pp. 1209-11, will show that generally some were observed on the plots that did not 
come into the samples, though such occurred in very insignificant amounts. The 
average number of species over the four years was, on plot 3, 49, on plot 12, 49, 
and of course on the two plots, also 49. 
It is further seen that the number of species of grasses was, on plot 3—18, 15, 17, 
and 1 1 ; and on plot 12—16, 16, 17, and 16 ; the average number being therefore rather 
the higher on plot 3. Leguminosse are uniformly represented by four species in the 
samples from both plots. The number of species contributed by other Orders were, 
in the four years, as follows : on plot 3—28, 24, 28, and 31; and on plot 12—24, 30, 
29, and 30; the average number being practically the same on the two plots. 
It may be said that there is, upon the whole, a slight tendency to an increase in the 
number of species with the continuance of the unmanured condition; and that such 
increase as there is, is among the miscellaneous plants. It might indeed have been 
expected that, as the exhaustion of the soil increased, the competition arising from the 
luxuriant growth of particular species would have diminished in intensity, and have 
induced the results observed. 
Among the fluctuations from year to year the chief irregularity to be noted is that 
plot 3 had a large number of species in 1862, and a small number in 1867 ; whilst plot 
12 had a small number in 1862, and a large one in 1867. The reduction in number 
of species on plot 3 in 1867 was about equally divided between the grasses and the 
miscellaneous plants; while the increase in number on plot 12 in the same year was 
entirely in the miscellaneous plants. 
The table shows that there was a larger amount of undetermined matter in the 
earlier than in the later separations, and it is, of course, a question how such matter 
should be allotted. By careful examination in each case, it has been ascertained that 
by far the larger amount of the undetermined matter is referable to the grasses, and so, 
to bring the results of the different years into comparison, it has been thought fairer 
to include this matter among the gramineous herbage than either to exclude it from 
the record, or to allot it by judgment merely to the different divisions of Graminese, 
Leguminosse, and Miscellanese. With this explanation we may proceed to consider 
the results as they stand. 
Neither an examination of the tables now under discussion, nor of those including 
the results of the partial separations in other years, indicates any really marked 
increase or decrease in the percentage of the grasses in the total mixed herbage on the 
unmanured plots. There was, however, very considerable fluctuation in the percentage 
from year to year, according to season. Thus, in the first and the last of the com¬ 
plete separation-years 1862 and 1877, that is with an interval of 15 years, both the 
