118 J. O. HAGSTEOM, CEITICAL EESBAECHBS ON THE POTAMOGETONS. 



out of question because of the northern locality). The prominent midrib seems 

 to give preference to the former. The lateral nerves, on the contrary, are very feeble 

 just as in P. obtusifolius. The ligules are convolute and 9 — 10-fibrous in the front- 

 field. The very best proof of our combination, however, is given by the slender 

 turios which for the most part are transformed small branches, an intermediate 

 form between P. ohtusifolius and 'panormitanus. Further observations of those turios 

 will, no doubt, confirm my supposition. 



Distrihiition. Scotland, Marlee Loch, Devonian Isla, Co. Perth, 82, Stdrrock 

 (lib. Stockholm.). Rev. E. S. Marshall gives it also from Loch Schechernich, E. 

 Perth, 89. Other specimens named Sturrockii are not identic with this rare plant. 



P. obtusifolius M. & K. X pusillus L. (P. saxonicus n. hybr.). 



Folia linearia obtusa, magnitudine inter parentes medium tenentia, basi glan- 

 dulis oleiferis ut in P. obtusifolio. Turiones quam lis P. pusilli majores. 



It is very strange, that P. piisillus and P. ohlusifolms, so often seen together, 

 nevertheless so extremely seldom produce bastards. Among the innumerable forms 

 I have examined, it is only from two stations I have to record mules. One is 

 collected by Hubner and labelled »P. Berchtoldi b, folia latiora». The leaves are 

 really rather broad (2 mm) for a 2^i''Sittus-iorm, otherwise its habit presents the 

 greatest resemblance with this species. The prominent oil-cells (vittse) at the nodes, 

 the somewhat compressed stem, and, above all, the large turios with inner leaves a 

 little exceeding the sheaths prove, in the meantime, very clearly that its origin is 

 also due to P. obtusifolius. The leaf-apex is obtuse with a very insignificant cusp. — 

 The other is a Norwegian plant. 



Distribution. Germany, Heide, Saxony, 47, Hubner (lib. Stockholm.). — Nor- 

 waij, Katerud in Rakkestad, leg. H. C. Printz (hb. Christian.). 



P. oMusifolius M. & K. x trichoitles Cham. & Schl. (P. gallicus n. hybr.). 



Planta hybrida in omnibus partibus medium inter P. obtusifolium et trichoi- 

 dem tenens. 



Just as the two foregoing bastards, the present plant is also best known by 

 the propagating buds being quite intermediate between the two parent-species. The 

 sheaths surround here the inner leaves, the outer free leaves are short and stiff 

 reminding of P. trichoides. In size the bud is more like that of P. obtusijolius. The 

 leaves are narrow, 1,5 mm, with considerably sharper and more tapering apex than 

 the foregoing. The oil-lacunse are also here well developed. Ligules 8 — 9-nerved in 

 the front-field, convolute. The stem has a somewhat compressed form (intermediate), 

 the epidermis-cells are short as in P. trichoides, and the central cylinder has a more 

 or less oval cross-cutform and the bundles conspicuously disposed like P. obtusifolius. 



