1302 
MESSRS. J. B. LAWES, J. H, GILBERT, AND M. T. MASTERS, 
Saxifraga, Achillea Millefolium, Centauvea nigra , and Rumex Acetosa. In insignificant 
amounts, but still in most seasons present and notable, are Cerastium triviale , Poterium 
Sanguisorba (on plot 3), Leontodon hispidus, Veronica Chamcedrys , and Car ex prcecox. 
The remainder of the miscellaneous species occur less regularly, and in still smaller 
proportions, as will be seen by an examination of the tables. 
Comparing the mean results for each plot, it may be noted that Plantago lanceolata, 
Luzula camprestns, Pimpinella Saxifraga , and Leontodon hispidus are, on the average, 
more prominent on the poorer plot 3, whilst Conopodium denudatum, Rumex Acetosa, 
Achillea Millefolium , Centcmrea nigra, and Cerastium triviale are the more prevalent 
on the plot 12. 
Referring now, not to the prevalence of individual species, but of the species 
collectively of different families, it is seen that Plantaginacece have, on the average of 
the two plots, yielded the largest both percentage and acreage amounts among the 
miscellaneous plants. The Umbelliferce and Composites came second and third, the 
Ranunculacece fourth, and, after these, Polygonacece and Juncacece. Comparing the 
two plots, the Plantaginacece are decidedly the more prominent on the poorer plot 3 ; 
whilst the Composites and the Polygonacece are so on the less exhausted plot 12. 
Upon the whole it may be said that there is a tendency to increase in the number of 
species on the unmanured plots ; and the greater the exhaustion, the less will the grasses, 
and the more will the Leguminosse, but especially the miscellaneous plants, predominate. 
Among the latter, those which become the more prominent are referable to families 
noteworthy for the large numerical proportion in which either their specific or then- 
individual representatives occur in temperate climates, under natural conditions; that 
is in the absence of stimulated luxuriance, and consequent intensified struggle. Thus, 
of the widely distributed families, we have nine species of Composites, three of Um¬ 
belliferce, four of Rosacece, four of Ranunculacece, and three of Labiates ; whilst some 
of the smaller families, which have fewer species, are remarkable for the large quantity 
yielded by their individual representatives, as Polygonacece and Juncacece. 
Natural rotation. —Having now considered the climatal conditions of the four 
separation-years, the characteristics of the chief species found on the various plots, and 
in detail the number, percentages, and actual weights, of the species occurring on the 
unmanured plots, we are in a position to appreciate the facts in reference to what 
has been called natural alternation or rotation, as a result of the struggle uninfluenced 
by the artificial conditions induced by manuring. 
The conditions of success are so variable, even for the same plant at different stages 
of growth, and in different seasons, that we can scarcely predicate with any certainty 
whether any individual species will gain or lose in the conflict; although we may, 
perhaps, form a fair conclusion as to the prevalence of certain groups of species : as, for 
instance, the poorer grasses—one or other of them according to the wetness or dryness 
of the season or series of seasons, and also according to the decline of the freer- 
