nial plants of temperate regions, which are those considered in his 
second memoir. So he leaves the study of atmospheric vapor and 
plant hfe to the future, while confining himself at present to the 
relation between raizfall and the periodic phenomena of vegetation. 
It is not necessary to reproduce the tables of normal monthly rain- 
fall given by Linsser for each of his stations, and generally based 
upon many years of observations. Of course, these numbers express- 
ing the local rainfalls are, as is well known, less directly applicable 
to a neighboring locality than are the mean monthly temperatures, 
and they must be used with correspondingly less confidence. 
The constant fractional part of the annual sum total of heat, as 
previously established by Linsser, afforded him a valuable suggestion 
or a working hypothesis as to the relation between the life of the 
plant and other factors, such as sunshine, rainfall, nutrition, and in 
fact every factor that influences the hfe of the plant. If, namely, a 
plant utilizes one-tenth of its annual cycle of heat in order to bring 
it to the leafing stage, why may it not also require one-tenth of its 
annual cycle of rain or sunshine or some similar constant fractional 
part? Now, in the development of a plant there is necessary, first, the 
material, viz, rainfall, or irrigation water with the nutrition con- 
tained therein, and on the other hand one or more forces, such as 
sunshine and heat, by the help of which the plant can utilize that 
material in its process of assimilation. The different phases of the 
development of the plant, such as the appearance of the blossoms 
and the ripening of the fruit, are work accomplished; in this work 
the water supplies the principal material, while the heat, says Linsser, 
plays the role of the principal force; but the work of the plant—that 
is to say, its progressive development—will only be in proportion to the 
force, so long as the latter finds a sufficient quantity of material present 
to insure the complete utilization of the force. Evidently a force that 
is competent to convert a certain quantity of material to the use of 
the plant will only be half utilized if only half of this quantity of 
material is present. In other words, the development of the plant 
goes on in proportion to the quantity of heat only so long as the plant 
has at its disposal the maximum quantity of material that can be 
worked over by this heat. 
Therefore any further investigations as to the relation of the life 
of a plant to its external factors must necessarily consider the dis- 
tribution of material with reference to the distribution of heat. In 
our present case it is the distribution of the quantity of rain with 
reference to the heat, and if such relative distribution is not considered 
then its omission is only permissible under the assumption that dur- 
ing the whole period of vegetation the material necessary to the 
growth of the plant is always present in such quantity that at any 
