The Life of the Plant. 205 
stamens of the grass of Parnassus, Parnassia palustris, 
lengthen in succession, and place their anthers on the 
stigma. 
The stigmas of some plants, as Azgnonza, Grativla, 
Martinia, |Mimulus|, &c., which are expanded at the time 
of pollination, close on contact. A similar phenomenon is 
exhibited by the stigmas of Zorenza astatica, which close 
immediately after pollination, open again in a few days, but 
_are then insensitive to further contact. A fuller discussion 
of the mechanism of these movements would take too much 
space ; but with regard to their purpose, it is obvious that: 
they are all closely connected with the sustenance and pro- | 
pagation of the plant. 
Those parts of plants in which there is generally a ten- 
sion of the tissues exhibit a constant increase and decrease 
in the degree of tension. Under the ordinary conditions of 
life, in which plants are subject to the alternation of day 
and night, the intensity of the tension declines from morn- 
ing till noon, and rises during the night, attaining its maxti- 
mum in the morning. The most beautiful illustration of a 
movement of this nature, and the most independent of ex- 
ternal influence, is furnished by the telegraph-plant, Des- 
modium gyrans,a southern Asiatic shrub. The leaves of 
this plant are trifoliolate, the central and largest of the three 
leaflets moving only in sunshine, and assuming besides 
different positions by day and by night; while the lateral 
leaflets, which are about one-sixth the size of the middle’ 
one, perform almost uninterrupted oscillations whenever 
the temperature exceeds 22° C., their apices describing 
an ellipse. These oscillations, which are often very active, 
so as to recur several times in a minute, do not, however, 
proceed uninterruptedly, but spasmodically, as if the plant 
were continually acquiring new strength, or overcoming an 
obstacle. Other species of the same genus show similar but 
less active movements. The most remarkable feature of 
these periodical movements is that they are apparently in- 
