108 Rhodora idies 
THE DIAGNOSTIC CHARACTER OF VALLISNERIA 
AMERICANA. 
M: L. FERNALD. 
Ir has become so fixed a tradition in North America that our fresh- 
water Eel Grass or Tape Grass is Vallisneria spiralis L. that very few 
students of our flora have made a critical comparison of the American 
plant and the true V. spiralis of Europe. The European species is 
found only from the Mediterranean region northward into southern 
and southeastern Europe and adjacent Asia, not in the northern 
portions of the continent nor the British Isles, and therefore, as an 
essentially Mediterranean species, is not to be expected as a widely 
distributed plant of temperate eastern North America. Our own 
plant is found in fresh waters from central Maine to South Dakota 
and south to Florida and the Gulf States. In 1803 Michaux described 
the North American plant as a distinct species, V. americana, as 
follows: 
“AMERICANA. V. foliis erectis: pedunculis non spiralibus. 
Obs. Folia minus quam in spirali elongata, stantia, inferne non angustata. 
Hab. In flumine Mississipi et in fluvio S. Joannis Floridae.” 1 
Subsequent authors for some years took up V, americana as distinct 
but added nothing particularly significant to the description until 
Nuttall in 1818 stated that the male peduncles are “very short” but 
that the plant is “ Apparently a mere variety of V. spiralis.” ? In 
1826 Torrey definitely treated the American plant as a variety, calling 
it V. spiralis, B americana and again stating the character pointed 
out by Nuttall, “sterile peduncles very short.” 3 After Torrey’s 
publication the varietal designation was soon dropped and our plant 
has subsequently been treated as quite identical with the European. 
It is not perfectly clear that Nuttall and Torrey, in speaking of the 
short peduncle of the staminate inflorescence, were contrasting it 
with the peduncle in the European for they may have intended merely 
a contrast with the long peduncle of the pistillate flower which becomes 
in fruit more or less spiralled. 
1 Michx. Flor. Bor. Am. ii. 220 (1803). 
2 Nutt. Gen. ii. 230 (1818). 
3 Torr. Compend. 365 (1826). 
