Effects of Frost on Plants. 19 



October was nearly 2° below the average of its temperature, and 

 consequently did not contribute its usual share towards maturing 

 the wood of the season. November was fully 3° below the mean. 

 December was seasonable during the first fortnight ; but a most 

 remarkable change took place after the 15th. The mean tem- 

 perature of the last sixteen days of the month was 46° ; instead 

 of the temperature which usually occurs at the winter solstice, 

 this corresponds with that generally experienced even after the 

 vernal equinox. The rise of temperature above that of Novem- 

 ber, was also greater than what takes place between March and 

 April. The thermometer was seldom below 40° at night, and 

 never at freezing. These circumstances all contributed to bring 

 on excitement in the fluids of plants, as was evidently manifested 

 in the production of young shoots by many species. On Christ- 

 mas day the thermometer in the shade stood at 54^°. In the 

 beginning of January the weather was slightly rainy, and so unu- 

 sually warm that the lowest temperature observed on the 2d of 

 the month was 41°, and for each of the four first days the ther- 

 mometer marked 48° in the day, the wind blowing from the S. 

 and S. W. On the 5th the wind shifted to the N. W. and the 

 temperature began to fall, but up to the 7th the thermometer did 

 not sink below 27°. After this the winter may be said to have set 

 in ; the weather continued to increase in severity until the night 

 between the 19th and 20th, when it arrived at its greatest inten- 

 sity, and the thermometer sank in the morning of the 20th to 

 — 4^°, the ground being scarcely covered with snow." 



The temperature quoted is from a thermometer placed under 

 ordinary circumstances, but when the thermometer was cut ofi" 

 from the influence of heat from surrounding bodies, the tempe- 

 rature was shown to be much lower ; as appears from a subjoined 

 table of observations upon a radiating thermometer during the 

 month of January, in which the minimum temperature on the 

 19th is — 12°. Extended observations on the temperature as ob- 

 served in many parts of Great Britain, and its eff'ecis upon a great 

 number of plants follow, in connection with which Dr. Lindley 

 makes the following important remarks. 



" It is only by repeated observations of this kind that we can 

 hope for certain success in the important object of introducing 

 exotic species hardy enough to bear our climate ; consequently, 

 to multiply and systematize such observations is one of the most 



