154 
EOTAL HOETICTJLTUEAL SOCIETY. 
results witnessed ; but, unfortunately, there are no means of eli- 
minating the effects produced by one set of causes from those 
resulting from the other. 
It would seem probable that the comparatively rainless summer 
must have had considerable influence, the fluctuations in the rain- 
fall of the preceding season having been considerably greater and 
the absolute quantity also much larger. An inspection of the records 
of temperature, however, and especially of the variations in range and 
of rainfall, compared with the notes on the progress of the plants 
at the corresponding periods, does not show any general (but only 
occasional) correspondence. For instance, there was a great diff"er- 
ence in the range of temperature in the interval from May 16 to 
May 22 as contrasted with that in other intervals ; but there was no 
corresponding fluctuation observed in the growth of the plants at or 
immediately after that time. So, after the rainfall, no particular 
eftectswere observable, the quantity having probably been too small. 
These facts, if considered separately, would lead to the inference 
that the greater uniformity of soil-constitution, had more influence 
in producing the comparatively even growth than either the tem- 
perature or the rainfall. But this would be a most unsafe deduc- 
tion in the face of the many observations and experiments tending 
to show that the majority of plants, other conditions being equal, 
will accommodate themselves to almost any variety of soil*. Again, 
* In reference to this point it may not be irrelevant to allude to some experi- 
ments of Professor Hoffmann, of Giessen, an abstract of which, with comments, 
was given in the ' Grardeners' Chronicle,' May 14, 1870, from which we quote 
the following : — " In a previous set of experiments the Giessen Professor bad 
ascertained that the particular plants under observation grew equally well in all 
the varieties of soil in which they were placed, provided due care was taken to 
prevent the growth of intruding weeds. Having arrived at this result. Professor 
Hoffmann next left the several plants to themselves, with the view of ascertaining 
how they would comport themselves without assistance against the inroads of 
weeds. The result was that the weeds completely gained the upper hand, as 
might have been expected from their known habit. The species which held out 
longest was Asperula cynanchica. This plant, after having been grown in a bed 
for three years, and protected from the weed-invasion by the use of the hoe, was 
then left to take care of itself. It held out for four years, but was ultimately 
elbowed out by the intruders. Bearing in mind the principle of ' set a rogue 
to catch a rogue,' Professor Hoffmann then set himself to observe the results of 
the internecine struggle between the weeds themselves, thinking that the ulti- 
mate survivors would perhaps prove to have special affinities for the soil in which 
they grew. 
** Thus left to themselves the beds became so densely covered, that in a square 
