1 62 Dr, Smith’s Obfervations on the 
See Dr. Withering’s Botanical Arrangement of Britifh 
Plants. All thefe movements are, I think, certainly to be 
attributed to irritability. We mull: be careful not to confound 
them with other movements, which, however wonderful at 
fir ft fight, are to be explained merely on mechanical principles. 
The ftamina of the Parietaria , for inftance, are held in luch 
a conftrained curved pofition by the leaves of the calyx, that 
as foon as the latter become fully expanded, or are by any 
means removed, the ftamina, being very elaftic, fly up, and 
throw their pollen about with great force. I have lately ob- 
ferved a flmilar circumftance in the flowers of Medicago fal - 
cata. In this plant the organs of generation are held in a 
ftraight pofition by the carina of the flower, notwithftanding the 
ftrong tendency of the infant germen to affume its proper fal- 
cated form. At length, when the germen becomes ftronger, 
and the carina more open, it obtains its liberty by a fudden 
lpring, in confequence of which the pollen is plentifully fcat- 
tered about the ftigma. The germen may at pleafure be fet at 
liberty by nipping the flower fo as gently to open the carina, 
and the lame effeft will be produced. 
As the foregoing experiments fhew vegetables to poflefs irri- 
tability in common with animals, fo there are plants which 
feem to be endued with a kind of fpontaneous motion. Lin- 
naeus having obferved that the Rue moves one of its ftamina 
every day to the piftillum, I examined the Rut a chalepenjis , 
which differs very little from the common Rue, and found 
many of the ftamina in the pofition which he defcrlbes, hold- 
ing their antherae over the ftigma ; while thofe which had not 
yet come to the ftigma were lying back upon the petals, as well 
as thofe which, having already performed their office, had re- 
turned to their original fituation. Trying with a quill to 
* ' ftimulate 
