INTRODUCTION. 



XV 



called upon to feed the young leaves that their powerless condition 

 was made manifest." 



M. Duehartre, in his report of the winter of 1879-80, (p. 102) quotes 

 M. Voiron as testifying to this " slow mortality ;" who writing in the 

 month of May, says that 15 trees which had apparently only suffered 

 slightly (compromis) in April, were then dead ; and he adds that 

 a succession of deaths proceeded till the Autumn. M. Alf. Cottin, of 

 Sannois, corroborates the remark and states that it is not rare to see 

 Apple trees dying with their fruit formed or even in maturity. 



It is well known to foresters and all planters that forest trees, such 

 as the Ash, frequently do not conspicuously show the full effect of in- 

 juries received till, it may be, several years afterwards. 



Again, with reference to Ground Temperatures, Dr. Lindley re- 

 marks,* after the winter of 1837-38 — "Nothing seems more gene- 

 rally to have excited surprise, than that so many plants, apparently 

 killed, spring up again from the roots. Hence it has been generally 

 said, that many species which would have survived, if undisturbed, 

 were thrown away. ... In all cases, the roots of trees suffer 

 from frost less than the stems, partly perhaps because the vitality of 

 a root is greater than j that of a stem, as Mr. Knight long since 

 shewed : but more especially because they are so much less exposed 

 to cold. That the earth, being a bad conductor of heat, should re- 

 main in winter at a higher temperature than the superincumbent 

 atmosphere will excite no surprise ; but probably few persons are 

 aware, to how small a degree the temperature of the earth is lowered 

 in this country, during even long continued and severe frost. . . 

 Thus, two thermometors have been buried in the earth, one at the 

 depth of 1 foot, the other at the depth of 2 ft., and their indications 

 have been noted daily. The ground was never frozen to the depth of 

 a foot in the Society's garden, even while the temperature of the sur- 

 face was as low as -4° -5, and it did not fall to within 5° of freezing 

 at the depth of 2 feet during the same period." 



A few instances of ground temperatures are mentioned in the 

 following reports, but a large proportion of plants are recorded as 

 killed to the ground ; while many of these are described as shooting 



* Report of Frost of Winter, 1837-38. Trans, Hort. Soc. 2nd Ser. Vol. iu 



