Aquatic Plants of Pennsylvania. Timothy A. Block
cross veins in the central portion of leaves more densely reticulate .............................. water-celery (Vallisneria americana), p. 253
Figure 2.5. Vein reticulation (not to scale).
D. reticulate network of cross veins uniform throughout the leaf .................................................................. arrowhead (Sagittaria spp.), p. 31
C. midvein more prominent than the other veins of the leaf; cross veins not readily visible ................................ bur-reed (Sparganium spp.), p. 61
B. leaves less than 20 times longer than wide
E. plants mat-forming
F. leaves acute at the tips .......................... pipewort (Eriocaulon spp.), p. 243
F. leaves rounded at the tips
G. leaves to about 2 cm long, in pairs along the stolons ....................................................................... mudmat (Glossostigma cleistanthum), p. 241
G. leaves mostly 2–5 cm long, in tufts of 5–10 along the stolons ................................................................. mudwort (Limosella australis), p. 14
E. plants not mat-forming
H. leaves rounded at the tips ....... water lobelia (Lobelia dortmanna), p. 251
H. leaves acute at the tips ................................ pipewort (Eriocaulon spp.), p. 243
A. leaves generally round in cross section, not strongly flattened, or leaves absent, only stems apparent
I. leaves or stems stiff and firm, holding their shape out of water
J. leaf bases expanded and containing spore sacs .................................................................................... quillwort (Isoetes spp.), p. 245
J. leaf or stem bases not containing spore sacs .......................................................................................................... spike-rush (Eleocharis spp.), p. 111
I. leaves or stems limp, not holding their shape out of water
K. leaves reduced to bladeless sheaths at the base of the stems; flowering stems with a single terminal spikelet....spike-rush (Eleocharis spp.), p. 111
K. basal leaves filamentous; flowering stems lacking a basal sheath, each bearing a single lateral spikelet .... bulrush (Schoenoplectus subterminalis). p. 53
Figure 2.6. Quillwort leaf with spore sac in the base (×3/8).
Figure 2.7. Bladeless leaf sheaths in a spike-rush (Eleocharis sp., ×1/4).
Key to Submergent Plants with Finely Divided Leaves
A. leaves and/or stems bearing small bladders ................................................................................................... bladderwort (Utricularia spp.), p. 255
A. leaves and/or stems not bearing bladders
B. leaves opposite or whorled
C. leaves pinnately divided ............... water-milfoil (Myriophyllum spp.), p. 280
C. leaves palmately divided, fan-like; the segments repeatedly forking
D. leaves remaining rigid out of water, often crowded toward the stem tips ................................................. coontail (Ceratophyllum spp.), p. 269
D. leaves limp out of water, not crowded toward the stem tips
E. submersed leaves with a distinct petiole; flowers white ............................................................ fanwort (Cabomba caroliniana), p. 272
E. submersed leaves without a distinct petiole; flowers yellow ............................................................ Beck’s water-marigold (Bidens beckii), p. 278
B. leaves alternate
F. underwater leaves pinnately divided; simple emergent leaves often present ............................................. mermaid-weed (Proserpinaca spp.), p. 273
F. underwater leaves palmately divided, fan-like; the segments repeatedly forking; emergent leaves never present ........................................................................... water-crowfoot (Ranunculus spp.), p. 275
Figure 2.8. Leaf form and arrangement (not to scale).
Chapter 3. Emergent Plants
Emergent species grow in shallow water at the margins of lakes or streams. These species are rooted below the water surface, but the stems, leaves, and flowers are mostly above the surface. Emergent plants often form a continuous band at the edge of the water at depths to about 1 m; the width of the emergent zone depends on the slope of the lake bottom.
ARROW-ARUM, TUCKAHOE
PELTANDRA RAF.
Arum Family—Araceae
| Arrow-arum, tuckahoe | Peltandra virginica (L.) Schott & Endl. |
Native
Rooted, emergent perennial
Arrow-arum is one of several emergent aquatic plants with large, arrow-shaped leaves. The plants consist of a cluster of long-petioled leaves that grow from buried vertical rhizomes. The strongly veined leaf blades are 5–20 cm long. Separate male and female flowers are packed closely on a fleshy stalk (spadix) that is enclosed in a tightly rolled green spathe. After pollination the flower stalk bends downward, pulling the developing fruits under the water surface, where the spathe eventually rots away, releasing the pea-sized fruits. The height of mature plants is up to 1 m.
Other emergent aquatic plants of similar stature and leaf shape include pickerel-weed (Pontederia cordata) and duck-potato (Sagittaria latifolia). Neither has a flower and fruit structure at all like arrow-arum. In addition, pickerel-weed has more rounded, heart-shaped leaves, and those of arrowhead are much thinner in texture and more variable in shape than arrow-arum.
The range of arrow-arum extends from southern Maine to Florida and inland to Michigan, Missouri, eastern Kansas, and Texas. In Pennsylvania it is found in the eastern and western portions of the state. Arrow-arum typically grows in water to 0.3 m deep in swamps and along the shorelines of rivers, lakes, or ponds. Flowering occurs from late spring through summer.
Native Americans used grated roots of arrow-arum in milk as a tonic for babies. Leaves, seeds, and fruits were also used for food. The fruits of arrow-arum are also eaten by wildlife, including waterfowl.
Peltandra virginica—leaf ×1/4
Peltandra virginica—inflorescence ×1/4