POLYGONACEOUS GENERA. 25 
inhabiting ponds and Jakes, the leafy part of the stem and also 
its leaves floating on the surface of the water, and another form 
growing on the ground, or at least on muddy shores, developing 
upright leafy stems, and exhibiting a very different foliage and 
inflorescence. 
It was until somewhat recently understood that in various 
parts of North America we have the same Polygonum amphibium 
with its two very dissimilar varieties aguaticum and terrestre. 
There were early though unsuccessful protests against the doc- 
trine that the European and American plants are specifically 
one; and latterly there has prevailed the view that the terres- 
trial plant is quite distinct, specifically, from the aquatic. 
The view reached by myself after years of observation upon 
living plants both at the West and at the East is, that we have 
a number of distinct species that are normally aquatic, and as 
many more that are normally terrestrial; and that our aquatic 
species, at least in several instances, appear as riparian plants 
with wonderfully changed foliage and inflorescence, and that 
several of our normally terrestrial species do, under certain con- 
ditions, develop aquatic branches with floating foliage, this also 
strangely altered from that of the terrestrial type, yet at the 
same time most unlike that of the truly aquatic species in gen- 
eral, 
I also suspect that some of the aquatic, or at all events some 
riparian species exist in even a third state, more strictly terres- 
trial, with a third set of strongly marked peculiarities of habit 
and foliage, and that in such third form the plants flower either 
very rarely or never at all. 
If this judgment of mine as to the behaviour of the plants 
be well founded, it will follow that the delimitation of species 
will be most difficult, so long as a number of the species are 
known in only one of the three of their possible phases, Never- 
theless, I am about to propose a very considerable number of 
new species; and shall found some upon the aquatic phase only, 
others some upon a riparian state only, as well as many more 
upon properly terrestrial plants. In the case of these last I am 
the less afraid of erring, knowing as I think I do, that these are 
more commonly of one phase only. But in the case of the 
