991 
its mother plant was sickly and its grandmother would have died at 
once. It was in recognition of this view that in the eighteenth cen- 
tury the botanical garden at Teneriffe was established (the so-called 
acclimatization garden at Durasno and the Colegan Garden at Oro- 
tava, at an altitude of 1,040 feet) in order to furnish a temporary 
resting place for tropical plants that they might accustom them- 
selves to a cocler climate preparatory to their cultivation in southern 
Europe. According to Déllen, the same principle is applied in the 
acclimatization garden at Algiers to tropical African plants before 
their transportation into southern France. 
As the guiding thought of his second memoir, Linsser now remarks 
that we must divide the vegetable phenomena of the world into two 
divisions, viz, those in which temperature controls the annually re- 
curring cycle of phases, as is the case in the Temperate Zone, and those 
in which moisture controls, as in the Tropical Zone. Thus, on the 
grassy plains of South America, where the year is divided into a dry 
and a wet season, the entire course of vegetation depends upon the 
latter; the hottest and driest season exerts upon the vegetable life an 
influence like that of the northern winter, bringing, namely, rest and 
even death. Such a contrast is even found at Madeira, where, accord- 
ing to Heer, the weeds of northern Europe begin to vegetate in the fall 
after the dry summer months of trade winds and when the first rains 
fall, whereas in the hottest summer time all these weeds slumber or 
die, as with us in winter. In the steppes of Orenburg, Russia, when 
the sun melts the snow in April, it starts the first sprouts and the 
blossoms, and by the beginning of May the vegetation of the steppes 
has attained its highest brilliancy, being distinguished by the great 
number of many-colored tulips, as has been so often described by 
travelers; but this beauty passes by with remarkable rapidity, and 
when in June the dry, hot summer of the steppes begins, all the ver- 
dure is dry and dead, and in place of the blossoms there are seen only 
the dry, empty hulls; so that the whole life of the plants on the 
steppes is condensed into the short space of eight weeks. 
We thus see that for large portions of the earth the heat as such 
ceases to be the principal regulator of plant life, and moisture becomes 
the controlling influence. 
It is evident that the life of plants depends upon both temperature 
and moisture. In situations where there is always sufficient moisture 
the influence that decides whether or not a plant shall develop is the 
heat ; but in regions where there is always sufficient heat that deciding 
influence is moisture. Therefore Linsser proposes in his second me- 
moir to first state the influence of heat on vegetable phenomena more 
precisely than he had previously done, and then to develop the influ- 
ence of moisture. 
