104 J. O. HAGSTEOM, CRITICAL RESEAECHES ON THE POTAMOGETONS. 



From Siveden we have to record only one locality: Scania, Ringsjon, 82, Nils- 

 son, fruiting, but probably this bastard (lib. Lund.). — France, Besangon, 70, Grenier 

 (hb. Uppsal.), Valleville, Eure, 55, Malebranche (hb. Stockholm.). — England, 

 Ponds near York, 81, Bennett (hb. Stockholm.), Shropshire, 86, Beckwith (hb. 

 Stockholm.). In some private herbaria I have seen plants which are likely to be 

 this hybrid, viz. from Denmark, Nybro kro, 99, Baagoe and from Starnberger See, 



03, M. V. ZUR MtJHLBN. 



The above enumerated forms exhibit evident relationship to P. panormitanus 

 and pusillus, but are very different among themselves as to their qualities. In habit 

 and branching they approach now this form, now the other. Their leaves are al- 

 ways stiffer than in P. pusillus, and tipped with sharper points. Turios, unfortu- 

 nately, seem to be pretty rare, but when present they resemble now more the one, 

 now the other of the parent-species. — P. dualis, of course, is easily to be confounded 

 with the hybrids pusillus X trichoides and panormitanus X triclioides. I have seen the 

 latter from Bavaria, where it is collected by Dr. Fischer at »Appendorf im Lauter- 

 grund* and at sLauterbach*. It is darker in colour, has more prominent leaf-points, 

 more abundant sclerenchyma etc., by which it evidently shows a near affinity to 

 P. trichoides, while the turios allow us to trace P. panormitanus. 



P. Ibadius n. sp. 



Gaulis compressus (2—2,5:1) elongatus, internodiis 3 — 5 (summis 7) cm longis, 

 subsimplex vel infra medium ± ramosus, dichotome prolongatus ramis spicigeris 

 1" — 2" ordinis internodiis longis (ad 9 cm) instructis. Folia linearia 3 — 5-nervia 

 basi angustata apice acuta ± acute cuspidata, caulina 50 — 100 X 2 mm, floralia 25 — 40 

 mm longa, numquam subnatantia, nervo medio badio prominente. Ligulce breves 

 caducae eglandulosse vel subeglandulosse, in spatio intercarinali 11 — 12-nervi8e. Pe- 

 dunculi breves ± 20 mm sequales. Spica subdensa 3 — 4-verticillata. Stylus rostro 

 brevi instructus, stigmate parvo rotundato. Fructus subglobosus parvus, 1,75 mm 

 longus, badius, dorso rotundatus, lateribus convexis, iis P. panormitani Biv. platy- 

 carpi simillimus. — Fig. 40. 



By the nervation of the leaves and the form of the fruit this species is very 

 closely related to P. panormitamis. It differs by the flattened stem, the elongated 

 upper branches endowed with long internodes [D-type), the broad and elongated 

 stem-leaves, by the involucral leaves never growing subcoriaceous, by the ligules 

 lacking oil-cells and being 11 — 12-fibrous in the front-field. The styles are a little 

 beak-formed above and the fruits more rounded. The turios consist of transformed 

 branches in bud-state in the lower axils; they are about 10 mm long with short ± 

 cuspidate appressed outer leaves and obtuser enclosed inner leaves. They resemble 

 in a high degree the turios of P. panormitanus and exiguus m. At first I there- 

 fore believed that P. badius could be classed with the former of those. Later the 

 differences have appeared too considerable and I now think it better to establish 



