114 



J. O. HAGSTROM, CRITICAL RESEARCHES ON THE POTAMOGETONS. 



P. oi'ieiitalis Hagstrom. 



lacks 



New Potamogetons, in Botaniska Notiser, 1908, 102 — 103, with figures (tops 

 of stem- and branch-leaves). — Fig. 49. 



The stem of this species is compressed (2,5 : 1) and shghtly furrowed or even 

 two-sidedly furrowed. The arrangement of the vascular bundles of the stele is the 

 same as in other kindred species and the stele diagram is oblong. The epidermis 

 a strengthening layer, but has rather strong subepidermal strands, which, how- 

 ever, do not continue in the peduncle. The four vascular bundles 

 in the peduncle run rather near to one another. The stem branches 

 dichotomously from the primary spike. 



The leaf has about the same shape and size as that of P. 

 atteniiatus. The lacunar system also is much the same, consisting 

 of three to four larger channels on either side of the midrib in 

 the basal part, conducted by 2—3 subepidermal bast-bundles as 

 the figure 49 shows. But the marginal strand has the usual faint 

 structure. In the basal part and more or less far above the middle 

 the stem-leaves usually are 5-nerved, the topmost third part, or 

 so, in general 3-nerved. The main side-nerves join the midvein 

 in the very apex. Ligules with large basal oil-cells and 8—10 

 intercarinal bast-bundles. 



To judge from the rather scanty materials the styles seem 

 to be enlarged above and the stigmas small, roundly oval. 

 Fruit is not yet seen, but the plant is undoubtedly nearly kindred 

 with P. pusillus L. 



Distribution. Japan, R. Tama, Musashi, 88, Making (lib. 

 Stockholm.). — Assam, Brahmaputra at Dilmgach, 1896, D:r Kings 

 Collector (hb. Haun.). China, Ichang (hb. Haun.). Probably in 

 the whole of East-Asia. 



Fig. 49. P. oflentalis 

 Hagsth. a, Ti'.ansverse sec- 

 tion of the midrib part of 

 •a stem-leaf, »/, and sir., as 

 usual, \^. B, Transv. seet. 

 of the peduncle, showing 

 the site of the bundles, ^j". 

 0, Pistil, side-view, y-. 



P. Preussii Ar. Bennett. 



Najadacege in the Flora of trop. Africa, VIII, 2, 1901, 222. — Fig. 50. 



Having had no opportunity to examine the young ligules of the original spe- 

 cimens, I rank the species here additionally and ad interim on account of the affi- 

 nity with P. Hillii, stated by the author. Besides, the stem-anatomy is congruent 

 to that of the South American P. Berteroanus, and the shape and structure of the 

 leaves correspond closely with those of P. orientalis. The affinity with the Compressi 

 does not seem to be greater in this species than in the group on the whole. The 

 leaf-form reminds also of that of P. rutilus. Pistils and fruits are not known to me. 



The stem is nearly terete and with a shallow furrow as the figure shows. 

 Along the epidermis a one-celled strengthening layer is arranged beside the usual bast- 



