INTRODUCTION. 
XXI 
thefe feed-veflels areincluded in the feminal valves, the ftraps 
are rolled round the placenta, in two oppofite fpiral direc¬ 
tions, as is exprefled at C, where they are beginning to un¬ 
roll ; at D, they are reprefented as farther difengaged ; at F, 
they are quite expanded ; and at G, the elaftic force of the 
filaments being quite exhaufted, they are at reft. This un¬ 
rolling of the ftraps or filaments, however, is not gradual, as 
I have reprefented it, but performed in an inftant, by a hid¬ 
den jerk j by which the feeds are thrown off with force, and 
committed to the air, where they float innumerable. JVhat 
is their ufe ? Certainly they are produced for other purpofes 
befides the propagation of the fpecies ; every perfect feed 
fpike produces millions of thefe, and yet the plant is propo- 
gated by the root; nay, fo rarely do the feeds anfwer the 
purpofe of propogation, in this family, that I could never 
yet difeover a feedling plant of any one of the fpecies. 
The fame obfervation holds good, in refpeeft to all the 
other Ferns, and to the Fungi; the multitude of feeds produ¬ 
ced by an Agaric or a Boletus, is innumerable ! is aftonifh- 
ing ! yet not one of ten thoufand anfwers the purpofe of pro¬ 
pogation. Is not the Air we breathe charged with them all 
the declining part of the year } Do we not receive them into 
our Lungs with every breath we draw } Whence proceed the 
Quinfies, 
