84 INFLUENCE OF TEMPERATURE ON THE PROGRESS OF VEGETATION. 
differs from that of forwardness of vegetation are the positions of 
the years 1881 and 1883. A short consideration of these years 
will, I think, make clear the meaning of their exceptional 
positions. 
The mean temperature of the first four months of 1881 was 
one degree lower than that of the same period in 1887, so that 
we might expect to find the season of 1887 more forward than 
that of 1881; but, instead of this being the case, 1881 was the 
earlier by three days, being six days behind the average, while 
1887 was nine days behind. 
In order to explain this it will be necessary to compare the 
weather of the early months of the two years. The year 1881 
began with the coldest January of which, I think, we have any 
record, the mean temperature being as low as 27°3 degrees. The 
four following months were not exceptional in their temperature, 
none differing more than 2 degrees from the average, and their 
mean being about the average. In 1887 the first three months ~ 
were each below the average, but, while January was much 
warmer, March was considerably colder than those months in 
1881; April and May were both colder, the latter by several 
degrees, than in 1881. 
From these figures I think it appears that a very cold January, 
if followed by a comparatively mild February, March, and April, 
has less effect in retarding vegetation than when the temperature 
is more evenly distributed, though the mean of the four months 
is the same. 
With regard to the year 1883, it is shown in the table to have 
been five days before the average in the forwardness of vegetation, 
being earlier than either 1880 or 1885, which both had warmer 
early months. 
The explanation of this lies, I think, in the fact that in 1883 a 
mild January and February was followed by a March, the coldest 
of which I have a record, the mean temperature being as low as 
34 degrees, or 6 degrees below the average of the ten years. It 
seems to point to the conclusion that after plants have, by a long 
spell of mild weather, been brought on to an advanced stage, a 
