lvi FLORA ORCADENSIS. 
before a dozen hours have passed. This is, I believe, 
why so many orders and families of flowers are not 
represented in our floral treasures. The orders of 
Malvacee and Nymphacece and the families of Arabis 
and Campanula are not represented by a single 
plant; whilst the larger families of Hypervcwm and 
Centawrea have only one each. These are only a 
few of the unrepresented families and orders. 
Meteorological observations have been made in 
the county for the long period of eighty-seven years. 
During this time the lowest temperature was 8’, 
which occurred on 18th January 1881. The highest 
was 76°,on the 16th July 1876. It is the temperature 
range for the same month rather than the absolute 
extremes that test the enduring power of plants. 
Durirg this year, 1913, January had a minimum 
temperature of 31°, and a maximum of 48°, showing 
a range of 17° February had a range of 15. The 
mean difference for March between day and night 
temperatures is only 8°, whilst at Nairn it is 13°. 
During April it is 9° in Orkney and 15° at Nairn. 
When snow falls during the earlier months, it gener- 
ally acts as a protective covering for plants; but in 
March and April the sun’s rays clear off the snow 
and leave the plants exposed to the killing influence 
of “black frost.” In 1906, the absolute temperature 
range for March was 30°, but this is exceptional, for 
it seldom exceeds 20°. 1895 was a year of great 
severity. The temperature ranges were—January, 
20°; February, 22°; March, 26°; and April, 30°; but 
snow fell, or covered the ground, for 24 days in 
January, 24 in February, 4 in March, and 5 in April. 
