KUNGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 55- N:0 5. 



133 



subepidermal strands pretty feeble, otherwise as in tlie pusilloids. Benealli the pri- 

 mary spike the central stele is nearly terete with a rounded crosscut-form, the bun- 

 dles indistinctly separated or quite fused with a single centra] cavity. The stele of 

 the stem-prolongation, again, has rather oval crosscut-form and the lateral bundles 

 distinctly separated from the median ones by mechanical tissue. The hypoderma of 

 the stem-prolongation often 2-layered to stiffen that spike-bearing organ. 



The lacunar system of the submersed leaves typically provided with subepi- 

 dermal strands in the lower surface (fig. 58, 

 C, str.) or sometimes lacking them (specimens 



from Madagascar and Kunene), in which case ^yU^T^Y^Hrf^/^i 

 the leaves become more flexible. 



These small anatomical differences toge- 

 ther with the different mode of prolonging 

 the stem, dichotomously or cincinnately, might 

 suggest other discrepancies not yet sufficiently 

 attended to. 



Distribution. Asia, Khasia Ind. or., 

 Hooker & Thomson (hb. Stockholm., Uppsal., 

 Lund.), Corea, Port Chusan, 59, Wilford (hb. 

 Stockholm.), sterile, pollen richly developed, 

 but to the greatest part of wrinkled grains! 

 Japan, 63, Maximowicz (hb. Stockholm.). 

 Africa, Madagascar, Humblot 330 (hb. Lund.). 

 The habit-figure in Graebner, Potamog. 1907, 

 47, fig. 14, A, seems to me to represent the 

 Madagascar plant. Natal, in riv. Umschlangwe 

 pr. Phoenix, 93, R. Schlechter, n:o 3125 (hb. 

 Ziirich, Stockholm.). N. O. Rhodesia, Bång- Fig. 59. p. raseyi bobb. a, Top of a submersed 



, T , ri f . . . , , - , „ _, stem-leaf, ' T 4 . B, Transverse section of a isubm. stem- 



WeolO-Lake, Chirm-lSland, 11, R. L. *RIES, Ieaf below the middle, >?». C, Marginal part of this 



N:o 1024; Kunene bei Humbe, 99, Baum (hb. J^.V l'^STSc£TS^Ä' 



dermis and its one-celled pseudo-hypoderma, I, lacunse; 

 in the middle the fonr vascnlar bundles, vb, r \" . E, 

 Pistil, side-view, '/'. F, Fruit, side-view, ,'. 



Stockholm.) v. major Benn. 



P. Vaseyi Robbins. 



Ap. Gray, Manual of the Botany of the north U. S., 1867, 485. Fig. 59. 



The stem of this species commonly prolongs itself by one or tvvo short spike- 

 bearing branches consisting of only one internode, by which the plant becomes very 

 few-spiked (1 — 3 spikes). The lower branches do not seem to come to a spike-bearing 

 development but determine themselves by turios. These turios can scarcely be di- 

 stinguished from those of P. javanicus and miduhihimo. They are usually small, 

 transformed branches in the leaf-axils. Submersed leaves 3-nerved traversed by 



