86 On the Use of Air-Vessels in Planis. 
it blows, it is covered with a treble vail to defend it from the in- 
fluence of the element ; and this defence it loses not till after it 
has risen above the water. All the species seem admirably to 
coincide in every particular. We have a native in this country, 
where the nights are colder in proportion, What reason, then, 
can possibly justify such a variation? Prosper Alpinus endeavours 
to prove that the Nymphcea Lotus is in every respect the same 
as a common lily, and adds that they all equally sink at night. 
Now we kuow this to be a mis/ake, as not one of the species 
flowering in England does so: but there is another reason that 
makes me suppose the observation of Theophrastus unfounded ; 
there is 70 mechanism to draw the plant hastily under the water. 
I have now for some years dissected plants, and I never yet saw 
a purpose of any kind effected without a very visible means to 
produce it. A stalk never bends, a leaf turns, or a corolla twists, 
without the’ muscles presenting themselves in a proper way to 
effect the purpose required. If the interior of the stem had been 
found with spirals sufficient to raise or contract it, I should have 
credited the account. The Ruppia maritima, which draws un- 
der the water soon after fructification is over, has a stalk formed 
with proper mechanism to act thus, In the Valisneria spiralis 
there is also an evident proof of its being made to be drawn un- 
der the stream ; but even in these two plants, they remain above 
the water till after the fructification is past. That the flower 
closes at night, and lays its head on the water, is certainly true ; 
but this is also to take care of the stamen and pistil; it is the 
general watchfulness of Nature to perfect that which is to insure 
the safety of the future seed, and even the lying down of the flower 
is to prevent the dew from entering where the petals close, lest 
it should hurt and explode the pollen too early; for, ata certain 
time of its formation, it bursts immediately on water getting 
through the stamen, and becomes (if not ripe enough) quite in- 
capable of performing its part in the fructification of the seeds. 
This very case seems to contradict the fact advanced by Theo- 
phrastus. But may I be so daring as to hint that neither Greeks 
nor Romans were very methodical in their accounts of the phe- 
nomena of nature? And though this famous Grecian is thought 
to be one of the most exact in whatever he records, yet his flesh- 
consuming stone, which he says destroyed in forty days all bat 
the bones of the body laid in it, and turned to stone the shoes 
and every other different material placed in that repository, 
shows that he believed ‘hat which he never took the trouble to 
investigate. As to Pliny, he credited that stones brought forth 
young; and he repeatedly mentions several sorts of firs that had 
tap-roots six cubits in length; though there is but one species ai 
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