i8o 
It is obvious, then, that the temperature ascertained by means 
of thermometers placed four feet above the ground, over short grass 
or snow, and sheltered by a louvred screen (Stevenson’s) from 
the direct and reflected rays of the sun, from radiation and 
evaporation, and very considerably from the wind, is the tem- 
perature of the air, but is very far from being the temperature 
to which plants exposed to all these influences are subject. 
When the open-air temperature is taken, it is seen that the 
average mean of our coldest month (January) is fully 45 0 , 
which gives sufficient heat to stimulate vegetable growth. 
The result is that during a mild winter flowers may be in 
bloom all the time in sheltered nooks, and even when the 
winter is perfectly normal a few bright warm days will cause 
vegetation to make a false start. It is no uncommon thing in the 
spring to see several different sets of leaves thus produced upon 
rose bushes. The variability of our winters is so great that a 
difference of two months in the time of flowering of many of our 
early wild flowers is not uncommon. 
Councillor J. D. Siddall, late President of the Chester Society 
of Natural Science, who has observed the flowering of our early 
plants for the past twenty-one years, gives the variations in time 
of flowering of four early plants as follows : — 
Earliest. Latest. 
Snowdrop 6th Jan., 1894, !898 ... 20th Feb., 1900 
Celandine (R.Ficaria) 18th Jan., 1898 ... 5th March, 1900 
Crocus 14th Jan., 1884 ... 19th March, 1886 
Coltsfoot 3rd Feb., 1898 ... 16th March, 1900 
Besides the shade and open-air temperatures, that of the ground 
itself plays a not inconsiderable part in determining the character 
and development of plants. The following figures give the months 
with mean temperatures below 42 0 : — 
UNDERGROUND MEAN TEMPERATURES, ONE FOOT 
BELOW THE SURFACE, IN ORDINARY SOIL. 
December. January. February. March. 
Southport ... 40*7° ... 38*0° ... 38*1° ... 40*6° 
Chester 42*5° ••• 40 o° ... 38-3° ... 41-1° 
The foregoing are the principal extremes and means of tem- 
perature that call for remark. 
The following diagram shews the ways in which the tempera- 
ture within the area varies from month to month throughout the 
