107 
1. Ser. gramineifolia Hagstr. 
forma puyensis n. f. : caulis ca. 0,5 m altus ramosissi- 
mus, tennis; folia ramea submersa lanceolata obtuse cuspi- 
data minima, folia natantia numerosa, forma et magnitudine 
cum iis Pot. graminei congruentia coriacea; fructus rari, 
médiocres, majores quam in P. gra- 
mineo, quoad formam iis P. nodosi 
simillimi. 
This form is known from only 
one place, where it produces in each 
spike some few ripe fruits with em- 
bryo, thus beeing an excellent in- 
stance for the fact, that the Potamo- 
geton-bybrids really develop fruits 
with apparenly ripe embryo. For 
the present plant, if ever anyone, is 
a sure bastard, growing in only a 
single little spot of the whole world. 
At the first sight one recognizes in 
it P. gramineus. 1st collector also 
immediately took it for »P. hetero- 
phyllum DC. var.» Its small, ses- 
sile, lanceolate, slightly denticulate 
branch-leaves point undoubtedly and 
absolutely in this direction. But it 
is not quite of the same facility to 
decide who the other part may be. 
If there were no fruit developed we 
must much hesitate, but the form of the fruit aims to P. 
nodosus, the fruit-form of which among European species 
is singular. A closer examination confirms this supposai. 
The floating leaves being more coriaceous than those of P. 
gramineus, the submersed leaves more passing, the stipules 
longer and even more transitory, the fruit larger; and as 
to the stem-structure, there are only few (1—2) subepidermal 
bastb undies in the cortex. P. gramineus has 5—10, P. nodo- 
13 — 14. Pot. grami- 
neus L. X nodosus Poir. 
(P. argutus H.) ser. gra- 
minerfolia forma puyen- 
sis Hagstr. 13. Floral 
leaf, nat. size. 14. Fruit, 
magnif. 
