185 



mine the epoch of the awakening of the plants in the first two places, 

 but in the last mentioned the acceleration is forty-one days. This 

 acceleration is also very great at the other stations of England, as 

 well as at Valogne, which has also probably a sea temperature. 



It has also been impossible for me to fix the time of awakening for 

 places where the winter is the most rigorous, such as Lapland, 

 Sweden, and the United States. We have seen, however, that there 

 is twenty days retardation in places where the mean temperature is 

 very little below zero. Jever seems to be an exception to this rule; 

 but the results obtained in this place were only deduced from three 

 observations. 



The epoch of leafing corresponds, as we have said, with the end of 

 March and the month of April, and that of the flowering with the 

 months of ]May and June. The first includes the commencement of 

 spring, the other the end of it. Thus the temperature of Brussels 

 in spring is 10° C. The greatest variations besides are at Naples and at 

 Alais. It is also in these places that the leafing takes place first. 

 Venice, Parma, and Guastala are very little in advance, but the 

 month of March and the beginning of April are scarcely any warmer 

 than at Brussels. The dift'erence of temperature is only felt in a 

 marked manner in the following months. The flowering also takes 

 place about eighteen days sooner. 



Polperro, in regard to leafing, is about t^n days in advance. The 

 temperature in March is much higher than that of Brussels, while 

 in April it is about the same. The advantage is lost in the following 

 months, when, as regards flowering, Brussels is in advance of Pol- 

 perro, as well as of the localities in England. 



Brussels is about eighteen to twenty days ahead of the towns of 

 Holland and Germany in the epoch of leafing, and is behind in the 



complete to allow of undertaking such a task. The first chart would have shown 

 by a series of lines drawn over Europe the awakening of plants for each ten 

 days, that is to say, a first line would indicate the localities where the awakening 

 first takes place immediately after the coldest day of the year, which with us 

 is about the 20th of .January ; a second line would pass through places where 

 tlie awakening is on an average ten days later, and so on. Another system of 

 similar lines traced upon a second chart would have indicated in the same way 

 the, beginning of budding, always proceeding I)y intervals of ten days. We 

 should also have made similar charts for tiowering and ripening and the fall 

 of the leaves. By comparing these charts we should be able to see at a glance 

 the princii>al changes which take place in these various systems of lines. In 

 order to cimiplete this study we should imagine other systems of lines relating 

 to temperatures. Thus one system would show the localities in Europe where 

 frosts first cease, always advancing at intervals of ten days ; then iuiother sys- 

 tem for places which, at successive intervals of ten days, and beginning from the 

 awakening of the jtlants, have reached a sum total of temi)eratures amounting 

 to 18;^° JL\, corresponding to tlie epoch of leafing: further, a third system of 

 lines which should pass through places tiiat, counting from the time of awaken- 

 ing, have successively attained the total nunii)ei- of degrees of temperature 

 necessary f<n- the flowering of plants ; and so on for further systems. 



The charts relating to vegetation and those relative to teniperatiu'es would, by 

 comparing them, give much cinMous information. Unfortunately the observa- 

 tions we jiossess of daily temi)eratin'es are still as rai-e as those of the fiower- 

 ing. I have therefore been compelled to renounce that i)ortion of my work. 



