^ 9 TATION BULLETIN 524

A0.52H

BIO SCI
riJBJ^ARY

Aquatic Vascular Plants of New England:

Part 6. Trapaceae, Haloragaceae,

Hlppuridaceae

by
G. E. Crow and C. B. Hellquist

NEW HAMPSHIRE

AGRICULTURAL EXPERIMENT STATION

UNIVERSITY OF NEW HAMPSHIRE

DURHAM, NEW HAMPSHIRE 03824

Un|ver"iity of New Hampshire Library

5

^ 9 TATION BULLETIN 524

A0.5ZH

BIO SCI
-iJBi^ARY

Aquatic Vascular Plants of New England:

Part 6. Trapaceae, Haloragaceae,

Hippuridaceae

by
G. E. Crow and C. B. Hellquist

NEW HAMPSHIRE

AGRICULTURAL EXPERIMENT STATION

UNIVERSITY OF NEW HAMPSHIRE

DURHAM, NEW HAMPSHIRE 03824

University of New Hampshire Library

GioSa
S

no.5A4-

ACKNOWLEDGEMENTS

We wish to thank Drs. Susan G. Aiken and WilUam D. Countryman
for their helpful comments on the manuscript. We are also grateful to
the curators of the following herbaria for use of their collections: BRU,
CONN, CUW, GH, HNH, KIRI, MASS, MAINE, NASC, NCBS,
NHA, NEBC, VT, YU. A special thanks is extended to Pamela Bruns
who prepared the illustrations.

This work is a result of research sponsored by the New Hampshire
Agricultural Experiment Station. The NHAES reserves the right to
reproduce, publish or otherwise use, and to authorize others to use, the
work for Government purposes notwithstanding notice of copyright.

Copyright " 1983 by the University of New Hampshire. No part of this work may be
reproduced in any manner without permission from the authors and the University of
New Hampshire.

Programs of the New Hampshire Agricultural Experiment Station are open to all
persons without regard to race, color, national origin or sex. The University of New
Hampshire is an Affirmative Action/Equal Opportunity Employer.

UNH LIBRARY

3 ^tDDD DDhlfl Mfi7D

ABSTRACT

This paper is the sixth in a series of reports on the aquatic and
wetland flora of New England. It treats all species of the Trapaceae,
Haloragaceae, and Hippuridaceae occurring in New England and
includes keys, comments on taxonomy and nomenclature, habitat
and distributional information, water chemistry data, illustrations
and dot maps. Those species regarded as rare and endangered in the
New England Region or in one or more of the six New England States
are also noted.

KEY WORDS: Aquatic Plants, New England Flora, Taxonomy, Trapaceae,
Haloragaceae, Hippuridaceae, Trapa, Myriophyllum, Proserpinaca, Hippuris, Water
Chestnut, Water Milfoil, Mermaid Weed, Mare's-tail.

TABLE OF CONTENTS

Page

INTRODUCTION 1

TRAPACEAE 2

Trapa 2

Trapa natans 2

Selected References 2

HALORAGACEAE 5

Myriophyllum 5

Key to Species 5

Myriophyllum tenellum 6

Myriophyllum humile 6

Myriophyllum farwellii 10

Myriophyllum alterniflorum 10

Myriophyllum pinnatum 10

Myriophyllum verticillatum 10

Myriophyllum heterophyllum 11

Myriophyllum spicatum 11

Myriophyllum exalbescens 12

Proserpinaca 12

Key to Species 12

Proserpinaca palustris 19

Proserpinaca pectinata 19

Literature Cited and Selected References 19

HIPPURIDACEAE 23

Hippuris 23

Hippuris vulgaris 23

Selected References 24

u

Aquatic Vascular Plants of New England:

Part 6. Trapaceae, Haloragaceae,

and Hippuridaceae

by
G. E. Crow and C. B. Hellquisti

INTRODUCTION

This is the sixth in a series of reports on the aquatic and wetland
flora of New England. These reports are intended to aid conservation-
ists, fish and game personnel, consultants, botanists, and students in
the identification of aquatic plants. The coverage is strictly New
England but is of value throughout the northeast. Data have been
gathered from herbaria in New England and from personal field work.

Chemical data presented represent samples from many waters
throughout New England. The alkalinity readings are total alkalin-
ity, expressed as milligrams per liter (mg/1) CaCO,. The number of
observations are included in parentheses following alkalinity and pH
values. Since pH and alkalinity vary greatly during the day, the
values are only indicative of the water quality. Chloride values are
given where data are available and of value.

The rare and endangered plant lists referred to are those prepared
for each of the six New England states by the New England Botanical
Club in cooperation with the United States Fish and Wildlife Service,
Office of Endangered Species, Newton Corner, MA (RI — Church and
Champlin, 1978; MA — Coddington and Field, 1978; VT — Country-
man, 1978; ME — Eastman, 1978; CT — Mehrhoff, 1978; NH — Storks
and Crow, 1978). Taxa indicated as rare, threatened or endangered
for the entire New England Region are also noted (Crow et ai, 1981,
Rhodora 83: 259-299.)

We invite comments and/or criticisms on this treatment. Infor-
mation on any species omitted or any known localities not docu-
mented by us will be welcomed. If anyone is interested in specific
localities of any of the species indicated on the dot maps, please
contact us.

*Dr. Garrett E. Crow, Department of Botany and Plant Pathology, Nesmith Hall,
University of New Hampshire, Durham, NH 03824

Dr. C. Barre Hellquist, Department of Biology, North Adams State College,
North Adams, MA 01247.

TRAPACEAE

Trapa (Water Chestnut)

Floating annual, with slender roots; submersed leaves opposite,
finely dissected; floating leaves alternate, blades rhombic, petioles
inflated; flowers white, axillary among floating leaves; fruit a large
"woody" nut or caltrop with four sharp barbed spines.

1. Trapa natans L. Fig. 1, Map 1

Locally abundant, sometimes forming large floating mats, in
southern Lake Champlain, Vermont, and in the Sudbury and Concord
Rivers, and the Great Meadows National Wildlife Refuge, Concord,
Massachusetts. A native of Eurasia, this species has become a nox-
ious weed in the waters where it has become established. This taxon
was first introduced into North America about 1874 and was culti-
vated in Asa Gray's botanical garden at Harvard University in 1877.
By 1879 it had escaped to nearby Fresh Pond, Cambridge, Massachu-
setts (Countryman, 1977). Range extends from Massachusetts to
western Vermont, eastern New York, Maryland, and Virginia.

alkaHnity: mean 37.7 mg/1; range 12.0-127.5 mg/1; (5)

pH: mean 7.1; range 6.7-8.2; (5)

Selected References

Countryman, W. D. 1977. Water chestnut {Trapa natans L.) in Lake
Champlain. Proc. Lake Champlain Basin Environmental Con-
ference, Miner Center, Chazy, New York 4: 3-10.

Countryman, W. D. 1978. Nuisance aquatic plants in Lake Cham-
plain. New England River Basins Commission, Burlington, VT.
Lake Champlain Basin Study Tech. Rep. No. 23. 102 pp.

Muenscher, W. C. 1934 [1935]. Aquatic vegetation of the Mohawk
watershed, pp. 228-249 in: A Biological Survey of the Mohawk-
Hudson Watershed. New York State Dept. Conserv. Suppl. Ann.
Rept. 1934.

Smith, R. H. 1955. Experimental control of water chestnut {Trapa
natans) in New York State. New York Fish and Game J. 2:
173-193.

Winne, W. T. 1935. A study of the water chestnut, Trapa natans with a
view of its control in the Mohawk River. M. S. Thesis. Cornell
University, Ithaca, New York.

Figure 1.
Trapa nutans: A. habit of upper portion of plant with
floating leaves, x V4. B, habit, x Vs. C. basal portion with
caltrop (nut) attached, x V^.

1

ft a

I

HALORAGACEAE

1. Flower parts in 4's; fruit a schizocarp, splitting into four 1-seeded

nutlets (figs. 2-6); emersed leaves reduced, bracteate, less than 1 cm.

long.

1. Myriophyllum

1, Flower pgirts in 3's; fi*uit indehiscent, 3-angled (fig. 7); emersed

leaves foliaceous, several cm long (fig. 7).

^ 2. Proserpinaca

Myriophyllum (Water Milfoil)

Submersed or amphibious perennials (overwintering chiefly by
turions); leaves cauline, whorled or alternate, usually finely dissected;
flowers sessile, single in axils of leaves or bracts; fruit a schizocarp,
splitting into 1-seeded nutlets.

Key to Species

Leaves scale-like, roundish (fig. 2D) or absent.

1. M. tenellum

Leaves pinnately divided, segments filiform (figs. 3-6).
2. Flowers and fruits in axils of submersed leaves (fig. 3).

3. Fruits smooth, rounded on back or minutely papillate (fig.
3B,D), 0.7-1.2 mm long; plants submerged or amphibious; win-
ter buds (turions) absent.
2. M. humile

3. Fruits rough with prominent dorsal tuberculate ridges (fig. 3F),
2.0-2.5 mm long; plants always submerged; winter buds (tur-
ions) formed in fall.

3. M farwellii

2. Flowers and fruits in axils of emersed bracteate leaves, forming
an erect spike (figs. 4C,5A,5G).

4. Uppermost flowers alternate; leaves alternate or whorled.

5. Submersed leaves whorled; bracts entire or serrate, no more
than twice the length of the flowers.
4. Af. alterniflorum

5. Submersed leaves alternate; bracts pinnately divided, usu-
ally more than twice the length of the flowers.

5. M pinnatum

4. Uppermost flowers opposite; leaves whorled, or pseudo-
whorled.

6. Bracts usually more than twice as long as pistillate flowers.

7. Bracts pectinate to pinnatifid (fig. 51); winter buds well-
formed, clavate, abscissing by early winter and readily
dispersed (fig. 5G).
6. M. verticillatum

7. Bracts of upper portion of inflorescence serrate (fig. 5C),
somewhat pectinate at waterline (fig. 5D); winter buds
developed at the base of the stems or on rhizomes, usu-
ally remaining attached.

1. M. heterophyllum

6. Bracts usually less than twice as long as pistillate flowers.

8. Leaves feather-like; middle leaves with 12 or more seg-
ments on each side of rachis (fig. 6B); ends of uppermost
leaves flat-topped (fig. 6B); stem diameter below inflores-
cence thick, up to twice diameter of lower stem; turions
not formed.

8. M spicatum

8. Leaves not feather-like, often tangled in drying; middle
leaves with 11 or fewer segments on each side of rachis
(fig. 6F); ends of uppermost leaves rounded (fig. 6F); stem
diameter below inflorescence same diameter as lower
stem; turions formed in fall.

9. M exalbescens

1. Myriophyllum tenellum Bigelow Fig. 2, Map 2

Common in shallow sandy or muddy margins of ponds and lakes
of low alkalinity. This species occurs chiefly in the sterile submersed
form, flowering infrequently. Apparently tolerant of some salinity, it
has been observed in a coastal pond on Cape Cod, Massachusetts in
water with a chloride content of 1201.2 mg/1. The type locality is Fresh
Pond, Cambridge, Massachusetts. Range extends from Newfound-
land west to Ontario, Michigan, and Minnesota, south to Nova Scotia,
New England, Long Island, New York, and eastern Pennsylvania.

alkalinity: mean 7.2 mg/1; range 3.0-19.5 mg/1; (6)

pH: mean 6.6; range 5.9-7.2; (6)

2. Myriophyllum humile (Raf.) Morong Fig. 3, Map 3

Common, submersed or amphibious, in shallow acid waters of
eastern and southern New England. Extremely variable, three eco-
logicsd variants have been given nomenclatural recognition at the
forma rank. Range extends from Nova Scotia west, sparingly, to
Minnesota, south to New England, eastern New York, eastern Penn-
sylvania, and eastern Maryland.
Rare and endangered plant list: Vermont

alkalinity: mean 7.0 mg/1; range 2.5-13.0 mg/1; (19)

pH: mean 6.3; range 5.8-7.0; (19)

Figure 2.
Myriophyllum. alterniflorum: A. habit, x ^h. B. inflores-
cence, X 5. C. fruit, X 5.
Myriophyllum tenellum: D. habit, x i/^.

8

' — winter
bud

Figure 3.
Myriophyllum humile: A. habit of submersed plant, >< '/a.
B. fruits on submersed plant, x 5. C. habit of terrestrial
growth form, x 1. D. fruits on terrestrial plant, x 5.
Myriophyllum farwellii: E. habit of submersed plant, ^
^h. F. fruits, x 3.

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10

3. Myriophyllum farwellii Morong Fig. 3, Map 4

Uncommon in acid ponds and streams of northern New England.
Sterile plants of M. farwellii can be easily confused with M. humile
and M. alterniflorum. Positive identification requires fruit or presence
of turions. The black-spiculate vegetative character used by Fernald
(1950) to distinguish M. farwellii is sometimes observed in M. humile.
In New England M. farwellii is restricted to northern states, while
M. humile is chiefly distributed in southern New England. Range
extends from Newfoundland and Nova Scotia west to northern Mich-
igan and central Minnesota, south to Maine, New Hampshire, Ver-
mont, and central New York; British Columbia.
Rare and endangered plant list: New Hampshire

alkalinity: mean 7.2; range 3.0-9.5 mg/1; (3)

pH: mean 6.6; range 6.1-7.1; (3)

4. Myriophyllum alterniflorum DC. Fig. 2, Map 5

Widely scattered in lakes and rivers of northern New England;
uncommon to rare in southern New England. The leaf width varies
considerably. Plants with short compact leaves have been separated
as M. alterniflorum var. americanum Pugsley, but Aiken (1981) notes
that this condition appears to develop in low nutrient environments
and nomenclatural recognition is unwarranted. Range extends from
Newfoundland to Alaska, south to Nova Scotia, New England, north-
ern New York, northern Michigan, and northern Minnesota.
Rare and endangered plant lists: New Hampshire, Massachusetts,
Connecticut

alkalinity: mean 21.9 mg/1; range 5.0-78.0 mg/1; (17)
pH: mean 7.2; range 6.5-8.0; (17)

5. Myriophyllum pinnatum (Walt.) BSP. Fig. 4, Map 6

Rare, on peaty and muddy shores of southeastern Massachusetts
and Rhode Island. Last collected in 1951 in Falmouth, Massachusetts.
This species is found close to the ocean with the exception of the
Worcester County, Massachusetts population. Range extends from
southern New England west to West Virginia, Kentucky, Illinois and
Iowa, south to Florida, southwestern Oklahoma, and Texas.
Rare and endangered plant list: Massachusetts, New England

6. Myriophyllum uerticillatum L. Fig. 5, Map 7

Uncommon, in quiet waters of lakes and streams throughout
New England. This species was last collected in Connecticut in 1920
and in Massachusetts in 1943. It appears that it cannot compete with
more vigorous species of Myriophyllum, but may also be sensitive to
pollution. The best field characters for identification include bracts

11

that are always divided, or the production of the club-shaped winter
buds which are formed along the stem during the late summer.
Variety pectinatum Wallr. has long been applied to the New England
plants, but Aiken (1979, 1981) documents great plasticity in this
species and does not recognize this or any of the other varieties
described for this species in North America. Range extends from
Newfoundland west to Alaska, south to Nova Scotia, Connecticut,
Delaware, Maryland, the Great Lakes States, northeastern Texas,
Utah, and California.

alkalinity: mean 18.0 mg/1; range 5,0-39.0 mg/1; (11)

pH: mean 6.9; range 6.5-7.8; (11)

7. Myriophylum heterophyllum Michx. Fig. 5, Map 8

Locally abundant and aggressive in ponds, lakes, and streams in
New England. Populations of this taxon have recently become estab-
lished in northern New England in the Sebago Lake region of Maine
region and Lake Winnipesaukee, New Hampshire. The greatest con-
centrations of this plant are in southern Worcester County, Massa-
chusetts where it is well established in most waters. The populations
are so dense that boating, fishing, and swimming are hindered in
these waters. To the west of New England this species is typically
found in alkaline waters while in New England it has been restricted
to waters of low alkalinity. A small terrestrial form is often formed
when stranded on shore as the water level drops. Care must be taken
to avoid confusion of this form with M. pinnatum or terrestrial growth
forms of M. spicatum or M. verticillatum. Range extends from
southwestern Quebec, southern Maine, and central New Hampshire
west to Ontario, Michigan, and South Dakota, south to Florida, Okla-
homa, Texas, and New Mexico.

alkaHnity: mean 12.5 mg/1; range 3.0-33.0 mg/1; (29)

pH: mean 6.5; range 6.2-8.9; (25)

8. Myriophyllum spicatum L. Fig. 6, Map 9

Locally abundant and aggressive in alkaline waters of western
Vermont and Massachusetts, widely scattered elsewhere. This Eura-
sian species has long been aggressive south of New England. The
earliest record in New England dates to 1965 in Lake Champlain and
has become a problem in the Lake Champlain Valley of Vermont and
the Housatonic River Valley of Massachusetts. Weed irradication
programs have been instituted by many towns to rid lakes of this
weed. Three eastern New England localities have recently been dis-
covered: East Thompson, Connecticut, Framingham and Canton,
Massachusetts. These localities of low alkalinity are noteworthy as
they may indicate future problems with this species in the acidic
eastern waters. Range extends from Quebec and New England west

12

to Ontario, Michigan, Wisconsin, and British Columbia, south to
Florida, Oklahoma, Texas, Washington, and California; Mexico,

alkalinity: mean 60.0 mg/1; range 12.0-102.5 mg/1; (16)

pH: mean 7.8; range 6.7-10.2; (16)

9. Myriophyllum exalbescens Fern. Fig. 6, Map 10

Scattered in alkaline regions of New England with the largest
populations in Aroostook County, Maine, western Vermont, and
western Massachusetts. This taxon has long been included as a
variety under Myriophyllum spicatum L. in the United States. While
both species occur in New England, the native M. exalbescens
appears to be on the decline in areas where non-native M. spicatum
occurs. Aiken et al. ( 1979) indicate a good character to distinguish the
two species is that the vegetative stem apices of M. spicatum. appear
tassel-like and are usually red, while those of M. exalbescens are
knob-shaped and generally lack the reddish color, except during the
time of winter bud formation. Range extends from Newfoundland
and southeastern Labrador west to Alaska, south to Nova Scotia,
New England, West Virginia, Michigan, and northwestern Kansas.
Plants collected south of the 0°C isotherm are likely to be M. spicatum
(Aiken, 1981), thus records from Texas, New Mexico, Arizona, and
southern California need reexamination.

alkahnity: mean 57.4 mg/1; range 13.5-123.5 mg/1; (19)

pH: mean 7.8; range 6.8-9.8; (18)

Proserpinaca (Mermaid Weed)

Submersed in shallow waters or emergent along shores of ponds,
lakes, and streams; growing from slender creeping roots; leaves alter-
nate, pinnatifid to serrate; flowers sessile in leaf axils, solitary or 2-5;
fruit 3-angled, 3-seeded, nut-like.

Key to Species

1. Leaves of emersed plants serrate or serrate to deeply pinnatifid to
pectinate (fig. 7A,B); submersed leaves divided, (fig. 7A).

1. P. palustris

1. Leaves of emersed plants all pectinate (to divided), never serrate
(fig. 7D); submersed leaves divided (fig. 7E).
2. P. pectinata

13

Figure 4.
Myriophyllum pinnatum: A. habit of terrestrial form, x
'/^. B. fruit on terrestrial form, x 2. C. habit of
submersed form with emergent inflorescence, ^ ^h.
D. fruits on submersed form, x 2.

14

Figure 5.
Myriophyllum heterophyllum: A. habit of submersed
form with emergent inflorescence x V>. B. submersed
leaf, X 1. C. flowers, x 1 '/i. D. fruits, x l'/2. E. habit of
terrestrial form, x '/2. F. leaf of terrestrial form, x i.
Myriophyllum verticillatum: G. habit of submersed
plant with emergent inflorescence, x '/2. H. submersed
leaf, X 1. I. fruits, x 11/2.

15

winter bud

Figure 6.
Myriophyllum spicatum: A. habit of submersed form
with emergent inflorescence, x Va. B. leaf, x 1. C. flow-
ers, X 2. D. fruits, X 2.

Myriophyllum exalbescens: E. habit of submersed
form with emergent inflorescence, ^ V2. F. leaf, x 1. G.
flowers, X 2. H. immature fruit, x 2. 1, mature fruit, x 2.

16

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19

1. Proserpinaca palustris L. Fig. 7, Map 11

Common in the more acid waters of northern New England and
throughout southern New England. This heterophyllous, amphibious
species exhibits considerable variability in vegetative morphology.
Submersed leaves are divided and tend to grade toward pectinate to
pinnatifid to serrate as the water level drops. Serrate leaves (adult) are
typically associated with flowering and fruiting. However, photo-
period appears to influence leaf morphology in emersed plants and a
reversion to the juvenile leaf form (pectinate) is related to short-day
photoperiodicity and suggests that plants which have been referred to
P. intermedia fall within the range of variability of this species
(Davis, 1967) .Therefore, we are treating P. intermedia Mackenz. as a
synonym under P. palustris. Fruit variability likewise lacks disconti-
nuity. Thus, varieties are not recognized in this treatment. Range
extends from Nova Scotia west to Minnesota, south to Florida, Loui-
siana, eastern Oklahoma, and eastern Texas.

alkalinity: mean 13.0 mg/1; range 2.5-100.0 mg/1; (14)

pH: mean 6.5; range 5.4-7.3; (12)

2. Proserpinaca pectinata Lam. Fig. 7, Map 12

Uncommon in sandy acid ponds of eastern New England. The
leaves all remain finely dissected whether the plants are submersed or
emersed. Range extends from Nova Scotia south mainly along the
Coastal Plain to Florida, west to southeastern Texas.
Rare and endangered plant list: New Hampshire

Literature Cited and
Selected References

Aiken, S. G. 1976. Turion formation in watermilfoil, Myriophyllum
farwellii. Mich. Bot. 15: 99-102.

Aiken, S. G. 1978. Pollen morphology in the genus Myriophyllum
(Haloragaceae). Canad. J. Bot. 56: 976-982.

Aiken, S. G. 1979. North American species oi Myriophyllum (Halora-
gaceae). Ph.D. thesis. University of Minnesota.

Aiken, S. G. 1981. An experiment relating vegetative morphology of
Myriophyllum alterniflorum DC. (Haloragaceae) to growth sub-
strate. Aquat. Bot. 10: 383-388.

Aiken, S. G., P. R. Newroth, and L Wile. 1979. Biology of Canadian
Weeds. 34. Myriophyllum spicatum L Canad. J. PI. Sci. 59: 201-215.

Aiken, S. G. and K. F. Walz. 1979. Turions oi Myriophyllum exalhes-
cens. Aquat. Bot. 6: 357-363.

20

Figure 7.
Proserpinaca palustris: A. habit of plant, upper por-
tion with terrestrial growth form, x V^. B. habit of ter-
restrial form with pinnatifid leaves, x ^/2. C. side and
top views of fruits, x 2.

Proserpinaca pectinata: D. habit of terrestrial growth
form, X 1/^. E. habit of submersed plant, x i^. F. fruit, x 2.

21

t5

^ c

"I

«e
O

I

00

I

22

Aiken, S. G. and J. McNeill. 1980. The discovery of Myriophyllum
exalbescens Fernald (Haloragaceae) in Europe and the typifica-
tion of M. spicatum L. andM uerticillatum L. J. Linn. Soc. Bot. 80:
213-222.

Aiken, S. G. and R. R. Picard. 1980. The influence of substrate on the
growth and morphology of Myriophyllum exalbescens and Myri-
ophyllum spicatum. Canad. J. Bot. 58: 1111-1118.

Burns, G. P. 1904. Heterophylly in Proserpinaca palustris. Ann. Bot.
18: 579-589.

Ceska, A. and P. D. Warrinton. 1976. Myriophyllum farwellii (Halo-
ragaceae) in British Columbia. Rhodora 78: 75-77.

Chagnon, E. and A. L. Baker. 1979. Distribution, growth, and phospo-
rus relationships of water milfoil in Lake Winnipesaukee, New
Hampshire. Univ. of New Hampshire, Water Resource Research
Center Res. Rep. No. 23. 100 pp.

Countryman, W. D. 1976. Lake Champlain's inland sea and the dis-
tribution of aquatic plants. Proc. Lake Champlain Basin Envi-
ronmental Conference, Miner Center, Chazy, New York 3: 85-91.

Countryman, W. D. 1978. Nuisance aquatic plants in Lake Cham-
plain. New England River Basins Commission, Burlington, VT.
Lake Champlain Basin Study Tech. Rep. No. 23. 102 pp.

Davis, G. J. 1967. Proserpinaca: photoperiodic and chemical differen-
tiation of leaf development and flowering. PI. Physiol. 42: 667-669.

Fernald, M. L. 1919. Two new Myriophyllums and a species new to the
United States. Rhodora 21: 120-124.

Fernald, M. L. 1950. Gray's manual of botany. 8th ed. American Book
Co., New York. 1632 pp.

Fernald, M. L. and L. Griscom. 1935. Proserpinaca palustris varieties.
Rhodora 37: 177-178.

Fassett, N. C. 1939. Myriophyllum (new varieties). Rhodora 41:
524-252.

Grace, J. B. and R. J. Wetzel. 1978. The production biology of Eurasia
watermilfoil {Myriophyllum spicatum L.). A review. J. Aquatic PI.
Managem. 16: 1-11.

Kimball, K. D. and A. L. Baker. 1980. Chemistry of water milfoil
tissue: seasonal variation in submersed apices. Univ. of New
Hampshire, Water Resource Research Center Res. Rep. No. 25. 75
pp.

Kimball, K. D. and A. L. Baker. 1981. Mineral dynamics of the
submersed macrophyte, Myriophyllum heterophyllum, and the
competitive interactions for nutrients between M. heterophyllum,

23

phytoplankton and the sediments in littoral waters. Univ. of New
Hampshire, Water Resource Research Center Res. Rep. No. 35.
101 pp.

Love, A. and D. Love. 1938. The American element in the flora of the
British Isles. Bot. Not. 3: 373-388.

Love, A. and D. Love. 1961. Some notes on Myriophyllum spicatum.
Rhodora 63: 139-145.

Manuel, C. Y. 1973. Morphological variation in Myriophyllum heter-
ophyllum. Master's thesis, Washington University, St. Louis.

Morong, T. 1891. Notes on North American Haloragaceae. Bull. Tor-
rey Bot. Club 18: 229-246.

Morong, T. 1891a. Myriophyllum farwellii. Bull. Torrey Bot. Club 18:
146-147.

Nichols, S. A. 1975. Identification and management of Eurasian
watermilfoil in Wisconsin. Wise. Acad. Arts 63: 116-128.

Patten, B. C. 1954. The status of some American species of Myriophyl-
lum as revealed by the discovery of intergrade material between
M. exalbescens Fern, and M. spicatum L. in New Jersey. Rhodora
56: 213-225.

Reed, C. F. 1977. History and distribution of Eurasian watermilfoil in
United States and Canada. Phytologia 36: 417-436.

Schmidt, G. L. and W. F. Millington. 1968. Regulation of leaf shape in
Proserpinaca palustris. Bull. Torrey Bot. Club 95: 264-286.

Wallenstein, A. and L. S. Albert. 1963. Plant morphology: its control in
Proserpinaca by photoperiod, temperature and gibberellic acid.
Science 140: 998-500.

HIPPURIDACEAE

Hippuris (Mare*s-tail)

Emersed or submersed perennial; growing firom rhizomes; leaves
whorled, entire, linear-attenuate; flowers sessile, perfect or polygam-
ous, axillary in middle and upper leaves; fruit a small, ovoid nut.

1. Hippuris vulgaris L. Fig. 7, Map 13

Locally abundant along damp shores or in shallow waters of
northern Maine, uncommon in New Hampshire and Vermont. Range
extends from Greenland west to Alaska south to Newfoundland,
Nova Scotia, northern New England, central New York, Indiana,
northern Illinois, Minnesota, Nebraska, and New Mexico.

24

Rare and endangered plant list: Vermont

alkalinity: mean 24.6 mg/1; range 12.0-49.5 mg/1; (6)
pH: mean 7.0; range 6.5-7.3; (6)

Selected References

McCully, M. E. and H. M. Dale. 1961. Variations in leaf numbers in
Hippuris. Canad. J. Bot. 39: 611-625.

McCully, M. E. and H. M. Dale. 1961. Heterophylly in Hippuris, a
problem in identification. Canad. J. Bot. 39: 1099-1116.

Map 13.
Hippuris vulgaris

25

Figure 8.
Hippuris vulgaris: A. habit of emergent portion of
plant, X %. B. submersed plant, x V^. C. section of aerial
stem with fruits, x IV^. D. fruit, x 5.

26
Station Bulletins of Botanical Interest

Grasses of New Hampshire. I. Tribes Poeae (Festuceae) and Triticeae
(Hordeae). A. R. Hodgdon, G. E. Crow, and F. L. Steele. Bull. No.
512. 1979.

The Flora of Plum Island, Essex County, Massachusetts. M. J.
McDonnell. Bull. No. 513. 1979.

Aquatic Vascular Plants of New England: Part 1. Zosteraceae, Pota-
mogetonaceae, Zannichelliaceae, Najadaceae. C. B. Hellquist and
G. E. Crow. Bull. No. 515. 1980.

Aquatic Vascular Plants of New England: Part 2. Typhaceae and
Sparganiaceae. G. E. Crow and C. B. Hellquist. Bull. No. 517. 1981.

Aquatic Vascular Plants of New England: Part 3. Alismataceae.
C. B. Hellquist and G. E. Crow. Bull. No. 518. 1981.

Aquatic Vascular Plants of New England: Part 4. Juncaginaceae,
Scheuchzeriaceae, Butomaceae, Hydrocharitaceae. G. E. Crow
and C. B. Hellquist. Bull. No. 520. 1982.

Aquatic Vascular Plants of New England: Part 5. Araceae, Lemna-
ceae, Xyridaceae, Eriocaulaceae, and Pontederiaceae.
C. B. Hellquist and G. E. Crow. Bull. No. 523. 1982.

Hiker Traffic On and Near the Habitat of Robbins Cinquefoil, an
Endangered Plant Species. R. E. Graber and G. E. Crow. Bull. No.
522. 1982.

Grand Isle

iamoille

Chillenden
Caledonia
Washington

Sullivan

Bennington

Berkshire

Fairfield

Barnstable

%~^ — Nantucket
^Dukes
^Bristol. MA
^Bristol, Rl
^Newport
^Providence
^Washington
^Windham