232 
ing time, while the dry season is the ripening time, Linsser gives the 
following general conclusions: 
There are two especial laws regulating the life of every individual 
plant, (1) the individual habit; and (2) the principle of economy. 
The application of these principles explains and gives us a better 
comprehension of the course of vegetation under the equator as well 
as near the pole. 
The principal factors in the life of plants that we have thus far 
considered are heat and moisture. If the former is that whose 
periodicity gives warning of the necessity of economy, then the 
whole life of the plant is intimately dependent on the course of this 
heat, as in the extreme north and the greater part of the Temperate 
Zone where the moisture is otherwise sufficient. If it is the moisture 
that is subject to large periodical changes and the question of sut- 
ficiency of heat becomes unimportant because of its uninterrupted 
abundance, then the cycle of vegetable hfe depends upon the peri- 
odicity of this moisture, as in Madeira. If, finally, the variations of 
the climate are such that there is sometimes insufficient heat and 
moisture, then the necessity of economy in the use of both of these 
materials is enforced, and in the course of the year the plant seeks to 
develop as far as possible in accordance with both these necessities, 
as in the Steppes of southern Russia and near Bokhara and in isolated 
shady locations such as mountain sides. 
The law of fractional parts of the total annual quantity of heat, as 
demonstrated in Linsser’s first memoir, is therefore now seen to be 
only a special case, for northern and temperate latitudes, of the gen- 
eral proposition just enunciated. The former was the first approxi- 
mation toward a rational theory of the periodical phenomena of vege- 
tation, just as this more general proposition is the second approxima- 
tion. 
We have thus far studied principally the differences in the life of 
plants due to differences of climate in different localities. It still 
remained for Linsser to study the peculiarities of the same plants in 
different years in the same locality, to which end his manuscript 
material already offered a sufficient basis. 
Of the questions proper to be considered in this second category, 
viz, the study of plant life as depending on temporary variations of 
local climates, Linsser enumerates the following as having already 
been taken up by him, viz: (1) The influence of cloudiness, insolation, 
and atmospheric pressure; (2) the especial influence of the various 
distributions of rain on the individual periods of vegetation; (3) the 
relation of the length of the day and the night, as also of light 
itself, on the plant; (4) the influence of the nonperiodic variations 
of temperature; (5) the influence of cold or warm winters on the sub- 
sequent summer’s growth; (6) the investigation of the sums of tem- 
