222 AMERICAN MIDLAND NATURALIST 
cm. wide: (some of the leaves are long and narrow, 3x12 cm.) 
obtuse or acutish at the apex rounded to cordate. As the leaves 
change to those of the terrestrial the upper part of the petiole 
is often winged with abrupt sinuses where it passes into the blade 
petioles often 4 cm. long. 
RIPARIAN PHASE. The plant not only fails to bloom in the 
aquatic phase but the aquatic plants are never to be found at 
blooming time. Aquatic branches are, by elongation in growth 
rapidly changed into riparian ones, which are strictly speaking 
only aquatic branches in the condition of transition to terrestrial, 
or terrestrials with the lower foliage passing into aquatic when 
the glabrous floating leaves are still present. Such riparian 
leaves are characterized as having the upper part of the petiole 
winged and with abrupt sinuses when the wing passes into the 
blade. 
The type of the aquatic I may designate as numbers 857a 
and 859a collected by myself at Millers, Indiana in pools along 
the old Indiana Harbor Railroad. June 1, 1911. Numbers 856ab 
and 859ab represent types of the riparian plants. The two num- 
bers are the same variety collected in different pools. Numbers 
856b and 859b and 859c are specimens in which the foliage char- 
acteristic of riparian and aquatic plants is absent due to the fact 
that the plants grew nearly out of the water. The plants are, 
of course, all sterile. 
The petioles of the riparian plants are sometimes quite long 
and this often is the case when the leaf-blades are quite of the 
terrestrial type. I deduce from the analysis of many different 
kinds of Persicarias that the length of petiole depends more on 
the available amount of moisture the plant can obtain, rather 
than actual immersion of the leaves, whereas the pubescence of 
the leaves depends on the extent of actual emersion. One will 
often find plants growing in boggy places with a large supply 
of water, but actually unable to float that have typically pubescent 
leaf blades with the long petioles of the aquatic leaves. 
PERSICARIA PRATINCOLA Greene, Leaflets, Vol. I., p. 36. 
AQUATIC or SUBAQUATIC PHASE. Plant at first free-floating 
but later assurgent with only the first and lower leaves glabrous ~ 
slimy; leaves long-petioled, long acuminate, truncate at the 
base 9-12c m. long 25—4 cm. wide; margins almost parallel 
