From: Matyas Buzgo buzgo at systbot.unizh.ch> on 1999.12.10 at 15:14:15(3919)
The question, when and how Pistia occurred first in the New World is
unanswered, and may stay unanswered. Pistia seeds are up to
2mm long and 1mm in diameter. So, they are NOT transferred by wind.
They are shed in a mucilaginous matrix, rather hidden by old leaves and
roots beneath the main mass of the plant. Soon, the matrix decays and the
seeds sink to the ground. The seeds stay at the ground until germination
Therefrom, it is not very plausible that bird dispersal of the seeds is
frequent, though it certainly occurs. However, main dispersal appears to
be by young plantlets Pistia produces on stolones:
The stolones break easily and the feather-shaped roots enhance the ability
of the plantlet to attatch itself to animals or objects, similar to other
aquatic plants (Salvinia, Phyllanthus, Azolla, Lemnaceae, many aquatics in
Thus: it is possible Pistia reached the New World without human help,
obviousely quite some time ago, and may be considered native. At least,
until the opposite is proved.