INTRODUCTION. 



meteorological data, forgetting that similar averages or means may result 

 from very different ranges of climatic conditions. It is the extremes of 

 temperature, moisture, &c., which determine the character of the vegeta- 

 tion of a locality or district, and these are also the conditions which de- 

 termine the character of a health resort. 



Plants and trees, moreover, may be looked on as natural registering 

 "weather-glasses" of different degress of sensibility. Some botanists 

 (Boussingault, Alph. de Candolle, Ch. Martins, De Gasparin, Harv6 

 Mangon, Hoffmann) assert that what may be termed the zero, or sta- 

 tionary condition of vegetation, is at 6° C. (about 42° F.), and that the 

 various phases of plant-life depend on the accumulated heat to which 

 they are exposed ; and many observations and calculations have been 

 made with the object of testing the truth of this theory, especially on 

 plants which are of economic importance.' In the present contribution 

 to the subject I have dwelt with the meteorological and phenological ob- 

 servations of twenty years as if they had been made in only one year, and 

 by the use of averages I have eliminated, as far as possible, any errors of 

 observation of either an instrumental or a biological kind.' In this way 

 the temperature equivalent of upwards of three hundred native British 

 plants has been determined, as has also, in a less definite way, their 

 moisture equivalent. The reverse of this is also true. The blossoming 

 of the various plants indicate the existence of their temperature and 

 moisture equivalents — facts of extreme interest and importance to farmers 

 and gardeners as well as meteorologists, which would be greatly enhanced 

 in value if we possessed a similar set of observations on the germination 

 of seeds and the ripening of fruits and seeds.^ 



The neighbourhood of Marlborough, where the observations entered in 

 the Diary were made, very nearly represents the average climatic con- 

 ditions of the cultivated parts of England, and it is therefore suitable as 

 a standard with which to compare local variations. The geological, 

 physical, and meteorological characters of the district are given on the 

 following page, and the meteorological observations show that the mean 



' See Etude sur la Marche des Phinomines de la Vigitatien en France en 1880 et 

 1881. Par M. A. Angot. Bureau Cent. M6t. de France. Annales 1882. 



Resultate der wichtigsten pflamen-phdnologischen Beobachtungen in Eurofa, nebst 

 einer Friihlingskarte, von Dr. H. Hoffmann. Anhang Dr. Egon Ihne die norwegischen, 

 •&C. Giessen : J. Ricker, 1885. 



Reports of the Phenological Committee of the Royal Meteorological Society, by the 

 Rev. T. A. Preston, 1875-85. London : Stanford. 



" To avoid as far as possible any cumulative errors, the data were worked out for each 

 year and then averaged. This will explain any want of consistency in the figures which 

 may appear. 



3 Some careful experiment observations are required to determine the zero or 

 stationary point of vegetation, which might be carried out by means of the microscope. 

 It probably varies somewhat in different orders of plants, and is no doubt in many of 

 them lower than 42° F. 



