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628 PHARMACEUTICAL BOTANY 
to one-third of a second apart will not produce closure of the 
halves, though a second stimulus that is from 1 to 120 seconds 
apart from the first will effect closure, also that it is not essential 
for the stimulus to be on one hair, that a prick sets off the trap 
at once due to liquid escaping from turgid cells and, further, that 
all muscle stimulants, mineral acids and ammonia effect closure 
of the trap. 
Among the insects caught by Dionea are earwigs, millipedes, 
flies, ants, wood-lice and dragonflies. The length of time 
required for the digestion of their softer parts and the absorption 
of the soluble products of digestion varies. During this time the 
trap remains closed. The power of digestion possessed by 
Dionea is more limited than that of Drosera, which has been 
known to capture and digest many insects in a shorter period of 
time. 
Aldrovanda vesiculosa, which might well be called a ““Submerged 
Dionza,” is a relative of the Venus Fly-Trap. It is a floating 
aquatic plant found widely distributed in shallow ditches and 
ponds over the old world from Europe to Australia but nowhere 
abundant. This plant is entirely devoid of roots, but possesses a 
slender stem which bears whorls of modified leaves at its nodes. 
Like the Venus Fly Trap, each leaf shows differentiation into a 
winged petiole ending in 5 narrow processes that connect with a 
terminal, rounded, incurved blade, divided into equal halves by 
a sensitive midrib, but the midrib projects beyond the summit of 
the lamina as a bristle. Long, rigid, spiny bristles extend from 
the petiole and are thought to prevent the approach of animals 
unsuitable as prey. The margins of each half of the blade are 
bent inward and their rims are studded with short conical teeth. 
Projecting from the upper surface of the midrib and along a line 
describing the inner third of the upper blade surface are a 
number of sensitive hairs and short-stalked, disc-shaped glands, 
while over the outer portion of the surface are to be noted a 
number of scattered stellate hairs. 
Larvz of aquatic insects and small species of Crustaceans 
such as Cyclops, Daphnia and Cypris, swimming by, occasionally 
brush against the sensitive hairs and the 2 halves of the blade 
close together, just as in Dionga, and the animals are entrapped. 
