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flowering season, particularly as regards Prague, where the tempera- 
ture in Xpril, May, and June isa little higher than that of Brussels. 
The retardation for stations in Sweden, the United States, and 
Lapland is sufficiently explained by an examination of the tempera- 
ture tables, and also in regard to the epoch of ripening (fructifi- 
cation). 
I have already had occasion to call attention elsewhere to the fact 
that the falling of the leaves (effeuillaison) depends less upon the tem- 
perature of the year than upon the effects of the first cold. Thus the 
leaves fall sooner in the north than in the south, unless they fall 
sooner here on account of a season of great dryness or excessive heat. 
It would be superfluous to consider the influence of the other me- 
teorological agents when we still possess so little information as to 
the mode of action of the principal cause, which, in our climate, 
dominates in some degree all the phenomena of vegetation. 
The temperature month by month at Geneva and Lausanne vary 
little from that observed at Brussels. The winter months there are 
a little colder and the vegetation is a little behind. Toward the time 
of ripening this ret tardation changes into an advance. ‘The tempera- 
ture, however, in spring and winter is no higher than that of Brussels. 
Is not this advantage to be attributed to the fact that Geneva and 
Lausanne, having a higher elevation, enjoy purer air and a more 
efficient solar radiation, ‘elements which are not indicated by the ther- 
mometer? By following the mode of calculation generally adopted 
one would say that the difference of latitude between Brussels and 
the two Swiss cities is compensated by their different altitudes. Ge- 
neva and Lausanne are 4° 30’ farther south than Brussels, while their 
elevation averages about 420 meters greater, which shows that a de- 
gree of latitude farther north is about equal to an increase in height 
of 120 meters. At Munich and Groningen the same plants flower 
almost simultaneously, yet their latitudes and elevations are very 
different. Munich is 5° 4’ farther south, but is 524 meters higher. 
Here again a degree of south latitude nearly compensates 100 meters 
of elevation. It is to be regretted that we do not know the annual 
temperature of Groningen. Berlin and Stettin seem to approach 
that locality very nearly in the natural epochs of their plants. In- 
deed there is very little difference in their latitudes, their elevations, 
and probably, also, in their temperatures. 
Carlsruhe and Brussels have about the same annual temperature. 
The winter and early spring are a little colder in the first than in the 
second of these cities, consequently the vegetation is a little later; 
on the other hand the months of April and May are warmer, there- 
fore, we see the vegetation changes its retardation into an advance. 
Carlsruhe is about 2 degeees. south of Brussels. For this reason 
alone vegetation should be about eight days in advance as at Paris; 
but on the other hand its altitude is about 300 meters greater than that 
of Brussels, and its vegetation should for this reason 1 be about twelve 
days later. Combining the effects of these two causes, Carlsruhe 
would still have a retardation of more than four days, which is con- 
firmed by experience for the first portion of the year; but in the 
second part we see ‘this retardation change to an advance of fifteen 
days. Should we not here again remark, as was done before, that, 
