84 



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



The lacunar median part of the leaf consists of the usual small lacunae round 

 the median vascular bundle. On either side of those small channels, in the lower 

 half of the leaf, run two rows of large lacunae and thin bast-bundles in the conjunctions 

 between the lacunar walls and the epidermis. On both sides of the lacunar part the 

 small strands run at rather short intervals from each other as the fig. 32, C, shows 

 looking outwardly like fine nerves. The var. Fauriei Benn. also has the same struc- 

 ture. The only difference is that the bast-bundles are considerably stronger, by which 

 the leaf grows stiffer and more resistive. 



The leaf-apex gradually tapers 

 and exhibits an asy metric form just 

 as P. polygonus and others (Fig. 32, 

 A, b). The base is somewhat round- 

 ed, sessile, not subpetioled. The 



nSn '(llllllllll'l lllililiiliillill style is short, but distinct, and a 



little incrassate upwards, as is the 

 case in a good deal of species, and 

 the stigma small, roundish-oval, not 

 covering the whole upper surface of 

 the style (Fig. 32, B). Pollen of 

 small grains, spherical. 

 D -t;, y-^r^{' )^)Ul ]/^-\ Distribution. Japcfw, Nippon 



'^ ^ prov. Nambu, 65, Ichonoski (hb, 



Stockholm.). It belongs to the easter- 

 most Asia, how far to the south and 

 north is not yet fully known. 



Fig. 33. P. sifbslbiricns Hagstr. A^ Transverse sec- 

 tion of a stem-leaf at the middle, y", m, raid-vein, n', 

 lateral vein, sir, bast-bundles, I, lacunar system. B, Top 

 of a stem-leaf, [. C, Lignle, f. i>, Pistil, J. E, Trans- 

 verse section of stem, '^j^, ep, epidermis, 7, lacunar system, 

 sir, subepidermal bast-bundles, cc, central axis. 



P. siibsibiricus n. sp. 



Caulis ca. 5 dm altus, compres- 

 sus (^) filiformis, 0,5—1 mm latus, 

 parum ramosus, supra spicam pri- 

 mariam vix prolongatus ramis spiciferis, internodiis 3 — 7 cm longis. Folia anguste 

 linearia, caulina ca. 2 mm lata, 40—60 mm longa; summa ± 40 mm longa, basi rotun- 

 data, apice cuspidata, 13 — 17-nervia vel ultra. Ligulce ca. 15 mm longse, obtusse, 

 badise, basi glandulosse, fissse, in spatio intercarinali 10 — 13-nervi8e. Pedunmdus com- 

 pressus sequalis, 20—35 mm longus. Spica ± densa 3 — 4-verticillata. Pistillum stylo 

 brevissimo, stigmate complanato rotundato expanso. Pollen parvum sphseroideum. 

 Fructus non visus. — Fig. 33. 



The anatomy of stem and peduncle is much the same as in the foregoing. 

 The stem is provided with subepidermal bast-bundles and deprived of hypodermatic 

 layer, in the peduncle the condition is the reversed: no strands but a 2-celled strength- 

 ening layer, which, beside the scattered position of the vascular bundles, makes the 

 peduncle obviously thicker than the stem. In P. oxyphylhis the stem and peduncle 



