184 



This table of average intervals shows how variable is the accelera- 

 tion of one place over another during the difl'erent seasons of the 

 year. This acceleration even often changes into retardation, conse- 

 quently the isanthesic lines are far from remaining parallel. AYe 

 therefore conclude that latitudes and longitudes are not the only 

 and principal causes which regulate the phenomena that are enga- 

 ging our attention, because these unchangeable causes could not pro- 

 duce different effects; it is the same with regard to altitudes, we 

 must only consider them as intermediary agents, and we shoidd 

 do wrong to take them as the basis of calculations for determining 

 the epochs of natural phenomena." Let us see whether temperatures 

 will give more satisfactory results. In order to facilitate the com- 

 parison I have gathered in the table (which unfortunately has not 

 been completed for all the localities)'' the average temperatures for 

 3^ears, seasons, and months.'' I must limit myself to consulting 

 these elements, as I have not the necessary data to compute the base 

 of daily temperatures and particularly to take the action of the sun 

 into consideration. This first work will perhaps make us feel the 

 incompleteness of the system of meteorological observations adopted 

 at present (1849) in Europe. I have also been obliged to exclude the 

 influence of the temperature of the earth, although it is absolutely 

 necessary to consider it, in order to treat, the phenomena of vegetation 

 in, a complete manner.'' 



The mean temperature in winter at Brussels is 2° C. The most 

 favored localities in comparison with it are Naples, Alais, and Pol- 

 perro (near Lands End, England). I have not been able to deter- 



o It will be uuderstood that I wish here to speali only of the actiou of geo- 

 graphical circumstances considered outside of the influence of temperature. 

 This action has been but little studied up to the present time, but it is well 

 worthy of our consideration. The following is what one of the most distinguished 

 living botanists of the present time has written to me on this subject : " The 

 distribution and extension of each species of plant over the earth shows us 

 that the plants in general and each species as a unit are subject to organic 

 changes dependent upon longitude and latitude. Each has a limited range; 

 between tliese boundaries it has its paradise, where it thrives best. The organic 

 changes which take idace in individual plants, if one compares those that are 

 native in different i)laces, are such that -we might presume that even their 

 rieriodic phenomena must be affected. For example, all plants are stunted in 

 height and in the number of their leaves toward their northern limit (or rather 

 polar limit). They change their general appearance in going from east to west 

 on the same parallel ; they alter as to the extent of inflorescence and the size 

 of flowers in going north or south on the same meridian. Now, as it is only 

 by means of these organs that the plant vegetates in the presence of the world 

 outside of it, it is necessary in our observations to begin with the relation of 

 those organs, or rather the consideration of the developed organs onglit to enter 

 into our notation of their vital action. It further follows from this that we 

 ought to study plants whose natural boundaries are known to us ; these are 

 the true barometers for vegetable life" [i. e., as the barometer is the measure 

 of the activity of the atmospheric forces, so the natural geographic boundaries 

 are the measures of the vital activity of plant life]. (Letter of M. de Martin's 

 Observation of periodic phenomena, " Mem. Acad. Royal," Brussels, Vol. XVI, 

 p. 11.) 



6 Further, it has sometimes been necessary to give the temperature of a neigh- 

 boring locality instead of that of the place itself : thus for the temperature of 

 Polperro I hjive taken that of Penzance, and the temperature of Makerstouu 

 has been replaced by that of Edinburgh, etc. 



c I have omitted these figures in my copy of Quetelet's table. — C. A. 



d I should have liked to supplement this work with maps showing the princi- 

 pal epochs in vegetation, but the collected observations are not yet suQiciently 



