KUNGL. SV. VET. AKADBMIBNS HANDLINGAE. BAND 55. N:0 5. 



251 



in distinction to tlie Natantes and the Luceiites, the stone-cells of which are very 

 thick-walled and hard. — Leaf-apex of P. prcel. always cucullate and the margin 

 smooth. 



Anatomically P. prcelongtis belongs to the species which are rich in scleren- 

 chyma, while P. perfoliatus, again, is a non-sclerenchymatous form and even lacks 

 the interlacunar ligular bundles in the stem-cortex. The former has consequently 

 very numerous bast-bundles in the stem as well as in the peduncle, in the midrib 

 of the leaf and in the ligules, to which may be added that P. prcelongus has also 

 a well developed ^t-endodermis in the stem, whereas P. perfoliatus has o-endoder- 

 mis. Judging from these and other facts P. perfoliatus seems to represent a more 

 primitive type than P. prcelongus. 

 It approaches also obviously to 

 P. densus. 



It may be remarked that 

 among all known species P. prce- 

 longus has the longest peduncles, 

 as much as 65 cm long. 



From the fossil occurrence of 

 the two species in Scanian peat- 

 mosses it is clear that P. perfoliatus 

 has immigrated to Sweden almost 

 immediately after the melting of 

 the land-ice and that P. prcelongus 



A, Lowest stem-leaf, -J, showing 



Fig. 116. A—F, Pi-telongus Wulf. 

 the form of the base of the 1 — 4 lowest leaves. i>, Pistil, side-view, 

 ^'{ ■ C, Transverse section of the fruit, '{-, I, lid, p, putaraen, f, epicarp. 

 has followed rather close upon its ■'^' P="' °f •■' transverse section of the stem, \», showing the position of 



the pseudo-hj'podermal strands, str, ep, epidermis, 7ip, the two-layered 

 pseudo-hypoderma, il, intercellular lacuna, vb, vascnlar bundle of the 

 ligular circle, inside which there are 3 — 4 circles of bundles, iv, inter- 

 lacunar wall. E, Surface section of the epidermis, \^. F, Transverse 

 section of the lacunar portion of a fullgrown stem-leaf {lower half), \°, 

 m, mid-bundle, vb, vase, bundle, sty, bast-bundles. G — H, P. perfoliatus 

 Folia Valde ■'-''' ^' Transverse section of the lacunar portion of an adult stem-leaf 

 (lower half), \^ (Obs! without bast-strands). //, Transverse section of the 

 fruit, Y) ^ lid, p, putamen, f, epicarp. (Of. 0!). 



heels. 



P. prcelongus sometimes varies 

 with strongly recurved leaves: 



f. curviitus n. f. 

 recurvata. 



The forms can, besides, be 

 ranked to any of the following varieties: latif alius Alpers, brevifolius Celak., 

 angustifolius Graebnbr with both stem- and branch-leaves very narrow, and elegans 

 Tis. with elongated leaves, 210 — 250 X 20 mm, and long internodes above. 



Distribution. P. prcelongus occurs locally through the whole of the Scandi- 

 navian Peninsula as far as Alton and South Varanger in the Norwegian Finmark, 

 64, Henschen (hb. Uppsal.), and the Russian Lapmarh, Nuortijaur, 83, Hollmbn 

 (hb. Stockholm., Lund.) and Imandra, 92, Kihlman (hb. Stockholm.). 



The most northern Swedish localities are: North-Bothnia, Kengis, 31, L^stadius 

 (hb. Uppsal.), leaves green, elongated and narrow, 200x20 mm, labelled ^P. grami- 

 neuni v. lanceolatum Lj^st. Vet. Acad. Handl., Kengis, 1831, sed semina nondum 

 visa. An nitens vestrum p. parte? Hartm. in Fl. scand. Ed. 2, prcelongum sed per- 

 peram traxit*. L^stadius has changed the name here to *lanceolatum^ instead of 

 »boreale' in Vet, Acad, Handl., probably in order to express the shape of the leaves : 



