106 
That is, however, a strange case, since the stem-anatomy of 
the Potamogeton-bastards mostly has caught impression 
from both originators. This form is for the rest disting- 
uished through the green-coloured elongated leaves, P. alpi- 
nus-like stipules, by floral leaves with sloping base but 
without petioles. Stem-leaves V,', - V- ' mm, brauch-leaves -T-' 
10— -lo 10 
mm, peduncle ca. 60 mm, spike 17 mm. 
The examined specimen leads its origin from West- 
Prussia, »Kreis Preussisch-Stargard bei Pelplin im Ferse- 
fluss», where it has been collected by Professor R. Caspar}* 
1. IX. 1886. 
Already Caspary ingeniously has suspected this plant 
to be a hybrid and labelled it »P. perfoliatus -f- rufescens 
(P. rufescens b) viridis Casp.)». Græbner, Potamogetonaceæ 
ap. Engler das Pflanzenreich 31. IV. 11. 74, still names it P. 
alpinus var. virescens Aschers, et Græbner but notes Pro- 
babiliter prolem esse æstimo». However he has joined it 
with forms from Hesse and Bavaria, that might be P. alpi- 
nus v. rivularis Hartm., Handb. 1820. 79., and before all 
overlooked the fine serrulation, forbidding to combine it with 
P. alpinus as a variety* or form. 
Potamogeton graminens L. + nodosus Poir. (P. argu- 
tulus n. hybr.) 
As characters common to the forms of this bastard 
the following can be held forth. 
Folia submersa lanceolata denticulis sparsis cito deci- 
duis, apice paulo quam in P. gramineo L. obtusiore. Stipulæ 
foliorum caulinium iis P. nodosi similes, longiores et citius 
putrescentes quam in P. gramineo. Structura anatomica 
caulis ad P. gramineum fortiter vergens. 
Two formseries occur: 
series graminei folia: caulis ramosus, folia ramea lan- 
ceolata sessilia. 
series nodosifolia: caulis simplex vel subsimplex folia 
± petiolata. 
