P0LT&0NA.CE0U8 GEKEEA. M 



inhabiting ponds and lakes, 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 aquaticum and terresire. 

 There were early though unsuccessful protests against the doc- 

 trine that the European and American plants are specifiGally 

 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 Bast 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, yei 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 



