OUR AMPHIBIOUS PERSICARIAS 213 
taking place at the present time, this group of plants ought now 
to be a subject of very interesting study. Some of the species 
are still normally amphibious in the true sense of the word, and 
able to pass rather quickly from one habitat to the other. In 
fact some, like P. mesochora and P. coccinea, may have the 
characteristic terrestrial and aquatic shoots on one rootstock. 
Others may have the characteristic foliage of both phases even 
on one shoot, the upper terrestrial and lower aquatic, as in P.- 
ammophila and especially P. grandifolia. In others as P. pratincola 
or P. flwitans one or other of the phases may be either completely 
obliterated or vestigal. 
Whether the law of mutation is a notable factor, will, it seems 
to me, be a rather difficult problem to ascertain, for seeds of 
Persicarias I have found hard to germinate successfully. Some 
attempts made have been witheut avail. I have not in fact, 
as yet found a single indubitable seedling of any member of the 
group, possibly because it may be difficult to distinguish 
any given plant from other water persicarias, such as P. Hydro- 
piper and P. hydropiperoides. Moreover, the difficulty, of forcing 
normal terrestrial phases of plants known to be normaily also 
aquatic, into the latter phase, offers difficulties directly propor- 
tionate to the pericds of time they were allowed to grow in one 
habitat exclusively without access to the other. In other words 
shoots cf P. mesochora for example will only bloom simultan- 
eously in both phases at the water’s edge. A plant too long kept 
from water and grown on dry scil exclusively, will even lose its 
power of blcoming as a riparian plant, and take on what may 
be considered as a sterile xerophytic phase, the pubescence of 
which in this case resembles that of a plant found by me at 
Studebaker’s woods and hereafter to be described as new. This 
pubescence of the xerophyte of P. mesochora lasts only during the 
early season and the plant later becomes glabrate like typical 
terrestrial plants of the above-mentioned species. Shoots of the 
new plant to be hitherto described retain such pubescence always, 
and even, on the contrary, become more so later in the season. 
As Dr. Greene has pointed out, the amphibious smartweeds 
have every one, at least potentially, several separate phases, and 
must be studied and described in their separate phases. As long 
as the manuals persist in describing only in part plants, which 
though resembling one another in one phase, are different essentially 
