184 
This table of average intervals shows how variable is the accelera- 
tion of one place over another during the different seasons of the 
year. This acceleration even often changes into retardation, conse- 
quently the isanthesic lines are far from remaining parallel. We 
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 should 
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 
years, 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 tol to deter- 
a@Jt will be understood that I wish here to speak only of tie action 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 these boundaries it has its paradise, where it thrives best. The organi¢e 
changes which take place in individual plants, if one compares those that are 
native in different places, are such that we might presume that even their 
periodic 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 parailel; 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 ought 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, 
jay) 2115)) 
»b 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 have taken that of Penzance, and the temperature of Makerstoun 
has been replaced by that of Edinburgh, ete. 
¢T have omitted these figures in my copy of Quetelet’s table—C. A 
@T should have liked to supplement this work with maps showing the princi- 
pal epochs in vegetation, but the collected observations are not yet sufficiently 
