188 THE VEGETABLE WORLD. 
production of heat. M. Ad. Brongniart has made some experiments 
on this subject which have become famous. At the time of open- 
ing, the flowers of the sweet-smelling Colocasia presented to this 
observer an increase of temperature that might almost be com- 
pared to an attack of daily fever. These attacks were repeated 
for six following days with a considerable intensity, and almost 
at the same hour ; for it was between three and six in the after- 
noon that this increase of temperature reached its maximum. 
Analogous phenomena have been noticed at the time of fecun- 
dation in the flowers of our common Arum (Arwm vulgare), of the 
splendid Victoria Regia, the Magnolia, and some other plants. 
It is impossible to conclude our remarks on the fecundation of 
plants without instancing the aquatic plant known as Vallisneria 
spiralis, which has long been the admiration of naturalists, while 
poets have sung its praises. The Vallisneria is a dixcious plant; 
that is, it has male and female individuals existing separately, in 
the tranquil waters of some countries in central Europe, pril- 
cipally France and Italy (Fig. 271). In the female plant the 
peduncle of the flower is very long, having the form of a spiral 
twisted thread-like filament. A few days before fecundation the © 
spiral turns untwist themselves, and the peduncle lengthens, until 
the female flower terminating it reaches the surface of the water, 
and floats on its surface. The male plant presents, on the con- 
trary, a.very short peduncle, which is not capable of any exten- 
sion; it bears a multitude of little flowers, provided with stamens 
only, and enveloped by a closed transparent spathe. At the time 
of full bloom the spathe is torn, the peduncle of the male flower 
severs itself towards its upper part, and the flowers separated 
from the stalk rise: all shut up, like very small white pearls; they 
float on the surface of the water, and proceed to open near the 
female flower, which seems to wait for them. When fecundation 
has been effected, the peduncle of the female flower contracts ; it 
brings together its spiral turns, and carries its ovary to the bottom 
of the water, in order to ripen its seed. ; 
This is a phenomenon which has always excited the just adml- 
ration of naturalists and observers of every class. I was initiated 
into the first elements of natural science, at the Lyceum of my 
native town by M. Joly, now professor of the Faculty of Science 
