KEY TO ISOETES of NEW ENGLAND

 

1

Leaves erect, stiff, brittle; macrospores with minimal ornamentation (northern, rare)

I. prototypus

1

Leaves pliable; macrospores with prominent ornamentation

go to 2

.

2

Macrospores with distinct spines (most common taxon by far)

I. echinospora

2

Macrospores ornamented with ridges, interconnected or not

go to 3

.

3

Macrospore ornamentation reticulate, forming regular cells

go to 4

3

otherwise

go to 5

.

4

Ornamentation ridges rounded, not much taller than wide, girdle smooth

I. acadiensis

4

Ornamentation ridges much taller than wide, no visible girdle

I. engelmannii

.

5

Macrospores homogeneous in size and shape

go to 6

5

Macrospores of varying size and shape, or proximal zone flattened

(a hybrid)

.

6

Macrospore diameter average > 0.6mm

I. lacustris

6

Macrospore diameter < 0.6mm

go to 7

.

7

Leaves mostly medium green, girdle obscure

I. riparia

7

Leaves mostly dark green, girdle visible

I. tuckermanii

 

- Don Lubin