536 



Daisy (Bellis perennis), it should be mentioned that a portion of the 

 grass was selected where a large group of daisies were fully in bloom, 

 arid within a foot of this another space where every daisy was care- 

 fully cut off from a circle of 1 2 inches, in the centre of which a 

 second thermometer was placed on the grass, so that these records are 

 very conclusive as regards the growing plant. 



Bearing upon this subject, it is proper to state, from a series of 

 experiments with thermometers placed in full sunshine on the grass, 

 and at 4 feet above the grass, that in winter the temperature on the 

 grass is always lower than at 4 feet, whilst in summer the reverse 

 takes place, the thermometers reading almost alike for a short time 

 in spring and autumn. To this circumstance may be attributed the 

 less striking results in hot weather, especially where the difference 

 between the grass and a flower is only from 1 to 2. 



Tables stating the details of the observations, which extended from 

 February 26 to September 19, 1859, and from the 22nd to the 27th 

 of March, 1860, are given in the paper. The author subjoins the 

 following as the principal results : 



Great differences occur from time to time in the temperature of 

 plants, and much depends upon the meteorology of the day, the dif- 

 ferences being usually greater with a cloudless sky than with one 

 which is loaded with cloud. The time of day seems also to operate 

 on some plants to a great degree ; as an instance, the Erica herbacea, 

 which between 1 and 2 P.M. had shown a warmth of above 5 over 

 that of the grass, by 3 o'clock was only 1 warmer, and by 4 o'clock 

 was colder than the grass. 



In the majority of instances grass is colder than flowers, as shown 

 by the following examples : 



1. Eleven observations on Daphne cneorum in comparison with 

 grass. 



The mean gives Daphne cneorum 1'2 warmer than grass. The 

 temperatures range between 41 and 73*3. In nine cases the tem- 

 perature was warmest over Daphne cneorum, the greatest difference 

 being 37. 



2. Thirty-nine observations on Gentiana acaulis in comparison 

 with grass. 



The mean gives Gentiana acaulis 2 warmer than grass. The 

 temperatures range between 41 and 89' 8. In thirty-four cases the 



