PLD AMERICAN MIDLAND NATURALIST 
ammophila and P. fluitans, is evident from the following. I have 
found the former most abundant at Millers, Ind. in pools which 
seem never to dry up quite completely. If there were but a matter 
of selective habitat to explain their identity, why would not P. 
ammophila venture out a few meters into deep water and bloom 
as an aquatic, rather than hug the shore and wait until the aquatic 
foliage is withered on account of drying up of the water, before 
it blooms solely as a normal terrestrial. In other words the 
habitat of P. fluitans is. present where P. ammophila invariably 
grows! P. fluitans is reported from Dune Park, but a few miles 
away. 
I have found it difficult in course of a number of experiments 
to force terrestrial phases to change to aquatic. The plants are 
invariably so shocked by the sudden change to water that they 
die. I have however succeeded in keeping P. ammophila in aquatic 
phases growing as such, without blooming of course, for many 
months. I have one such shoot that kept a few aquatic leaves 
all winter in a twenty gallon glass jar with some soil in the bottom, 
and that too in spite of the ravages of Oscillatoria that would have 
choked any other plant, as it actually did all the Myriophyilum 
shoots and Utricularia, as also in spite of water-snails that seem 
carefully to avoid touching the foliage of the smartweed for some 
reason or other. 
Though some forms of P. grandifolia and P. pratincola are 
quite indistinguishable at times, the aquatic phases could hardly 
be confused. Similarly P. rigidula in the same phase could not be 
mistaken for either, by the shape of its leaves. This plant has, 
however, a very characteristic pubescence in the terrestrial phase. 
Superficial observers in studying these plants sometimes overlook 
the fact that two different species growing close together may 
have shoots one as hairy as the other, yet the character or kind 
of pubescence may be totally different and usually not noticeably 
so without a hand lens. 
The fact that in some-:of the species of amphibious persicaria 
the aquatic plrase is to all appearance simply vestigial, found 
only early in the season, and only for a short time, never to be 
looked for at flowering period, shows that they are normally 
adopting a certain phase exclusively. How long ago this process 
of divergence of types was begun it is impossible to say. Students 
of phylogenesis would say, that as these developments seem to be 
