99 
5—6 lateral ones in all. Endodermis has typical ö-cells. 
Though well separated from P. alpinus it nevertheless appa- 
rently takes its place in the neighbourhood of that species 
particularly for the close conformity of the style and stigma. 
The examined specimen is signed: »Herbarium of the 
late East India Company. N:o 5605/5. Affghanistan. Herb. 
Griffith. Distributed at the Royal Gardens, Kew. 1862—63 . 
Potamogeton sisiiformis n. sp. 
Caulis ca. 1 m altus, ramosus teres, internodiis 4—7 
cm longis; folia omnia submersa membranacea, margine 
scabra, medio 7-nervia lanceolata summum foliorum flora- 
lium subpetiolatum reliqua sessilia, basi attenuato obtuse ± 
conspicue cuspidata; caulina 80 — 100 mm longa 10—15 mm 
lata, ramea minora, y-gy mm; vaginæ latæ 25 mm longæ 
nervosæ obtusæ subpersistentes ad basin costis humilibus; 
pedunculi subincrassati vel fere æquales 100—120 mm longi; 
spica primaria 8-verticillata 30 mm longa, stylus brevis 
stigma ut in P. gramineo (humilis ovalis) ; fructus non visus. 
The stem-structure of this plant resembles much that 
of P. Zizii, the endodermis-cells however being more slightly 
onesided thickened, here and there even with intermingled 
0-cells and the mechanical strands occurring only in two 
circles, one subepidermal and the other of vascular bundles 
in the innerangels of the auter airchannels. Central axis 
thus consists of 3 vascular areas = P. gramineus, lucens 
etc. Blade of the leaf is slowly tapering downwards, more 
abruptly to the apex. Prolongation of the stem consists of 
a system of branches of P — 2 d ordre with sessil leaves. By 
these unpetioled or at most subpetioled leaves, the short 
obtuse apex of the leaf and the above described stem-ana- 
tomy P. ziziiformis principally differs from the European 
and North- American P. gramineus -f- lucens (P. Zizii M. et 
K.), which it otherwise in highest degree likens. True P. 
lucens and gramineus are not found in S. America. P. 
brasiliensis Bennett might be a nearly allied species. It 
