OUR AMPHIBIOUS PERSICARIAS 237 
hirsute petioles and lower midrib. Base of the leaves obtuse or 
rounded: apex slightly acuminate or just acute; leaf broader 
usually near the middle or the margins subparallel for a consider- 
able distance. 
The plants with long internodes are found in grassy or sedge- 
covered places: the stocky leafy plant, in open sandy or muddy 
exposed places. Muddy or moist localities usually produce glabrate 
plants with leaves dark purple below, or with a v-shaped purple 
blotch above. The leaves are often 17 cm. long and the petiole 
not over 1 cm. The earliest leaves of terrestrials show a tendency 
to approach the shape, and often lack of pubescence, of aquatic 
phases, even when entirely removed from water. Good examples 
of the early summer terrestrial are Nos. 961 and 962 of my her- 
barium collected July 9, 1911 at Millers, Ind. 
SPRING AND EARLY SUMMER AQuaATIC PHASE. Leaves small 
always glabrous, purple beneath, yellowish-green above, 4-8 cm. 
long and 1~-1.7 cm. wide, obtuse or acutish at the apex, always 
cuneate at the base, oblong to elliptic-oblong. Whole plant, es- 
pecially growing foliage, slimy glabrous, ochrea margins only 
noticeable above on the stem, entire or erose and not ciliate unless 
aérial. Internodes 3.5 cm. or longer: stems, thin and wiry. 
The aquatic phase of P. ammophila resembles that of small 
plants of P. fluitans or P. canadensis. Perfect resemblance does 
not long exist, as the plant soon emerges from the water, and the 
stems become thicker and aérial in character. I have found a 
remarkable series of specimens growing on one rootstock in a 
small pool at Millers, Ind., along the Indiana Harbor Railroad, 
June 1, 1911. The series of plants numbering eleven sheets all 
with several plants numbered 840a to 840k, contains all the inter- 
mediate transition forms from the strictly aquatic sterile to the 
normal terrestrial, ali having been gathered not only from one 
small pool, but from one original rootstock! All the changes of 
the various organs of the plants as to pubescence, disappearance 
of parts, and appearance of others can thus be studied in their 
development under the changed conditions incident to the drying 
up of the pool. The terrestrials were found on the shore and 
transition forms at various distances into the deeper water of the 
normal aquatic. The specimens were not studied simply as dry 
herbarium plants, but selected after careful study of the spec- 
imens in the field. A mere glimpse over the series in order, is 
