118 J. O. HAGSTRÖM, CR1TICAL RESEARCHES ON THE POTAMOGETONS. 



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

 to give preferenee to the former. The lateral nerves, on the contrary, are verv feeble 

 just as in P. dbtusifolius. 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. obtusifolius and panormitanus. Further observations of those turios 

 will, no doubt, confirm my supposition. 



Distribution. Scolland, Marlee Loeh, Devonian Isla, Co. Perth, 82, Sturrock 

 (hb. Stockholm.). Rev. E. S. Marshall gives it also from Loch Scheohernich, E. 

 Perth, 80. Other specimens named Sturrockii are not identic \vi(h this rare plant. 



P. obtusifolius M. & K. pusillus L. (P. saxouicus n. hybr. 



}. 



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

 dulis oleiferis ut in P. obtusifolio. Turioncs quam iis P. pusilli maj öres. 



It is very stränge, that P. pusillus and P. obtusifolius, so often seen together, 

 nevertheless so extremely seldom produce bastards. Among the innumerable forms 

 1 have examined, it is only from tvvo stations I have to record mulcs. One is 

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

 really rather broad (2 mm) for a pusillus-iorm, otherwise its habit presents the 

 greatest resemblance with this species. The prominent oil-cclls (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 mcantime, 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, Humnkr (hb. Stockholm.). — Nor* 

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



I*, obtusifolius tö. & K. x trichoides Cham. & Schl. (P. galliens a. hybr.). 



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

 dem t enens. 



.Just as the two foregoing bastards, the present plant is also best known b}' 

 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 still' 

 reminding of P. trichoides. In size the bud is tnore lik< > thal oi P, obtusifolius. The 

 Leaves are aarrow, 1,8 mm, with considerably sharper and more tapering apez than 

 the foregoing. The oil-lacunce are also here well developed, Ligules s — 9-nerved in 

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

 the epidermis-oells are short as in /'. trichoides, and the central cylinder has a more 

 or Less oval cross-cutform and the bundles conspicuously disposed like /'. obtusifolius. 



