Platk 207.— POTAMOGETON OCHREATUS. 



Family NAIADACE^.] [Genus POTAMOGETON, Linn. 



Potamogeton ochreatus, Raoul, Choix, 13, t. 7 ; A. Bennett in Journ. Bot. xxv (1887), 178 ; 

 Cheesem. Man. N.Z. Fl. 750. 



Potamojeton ochreatus was originally discovered by M. Raoul, who, as surgeon- 

 aaturalist to the French frigate " L'Aube," which was stationed at Akaroa from 

 August, 1840, to November, 1841, and from January, 1842, to January, 1843, had 

 excellent opportunities of examining the vegetation of Banks Peninsula and the 

 neighbouring districts. After Raoul's return to France he pubhshed his discoveries 

 first of all in the " Annales des Sciences Naturelles " (series iii, vol. 2) ; but in 1846 

 he incorporated them in a work of wider scope under the title of " Choix des Plantes 

 de la Nouvelle Zelande," illustrated by thirty beautiful plates. A full description 

 of P. ochreatus appeared in this work, together witli a finely executed plate (t. 7). 



Many views have been advanced respecting the systematic position of 

 P. ochreatus. Sir J. D. Hooker, in the "Flora of New Zealand" (p. 236), suggested 

 that it was identical with the widely spread P. gramineus, and in the " Handbook " 

 he doubtfully referred it to that plant. Mr. Bentham, in the " Flora AustraUensis," 

 considered it to be a form of P. obtusifolius, Mert. and Koch, a determination which 

 has been repudiated by subsequent workers. Mr. Kirk, in his first exploration of 

 the Waikato River, expressed the opinion that it was identical with P. zostercefolius ; 

 but he subsequently arrived at the conclusion that it was a separate species, " equally 

 distinct from P. compressus and P. gramineus " (Trans. N.Z. Inst, iv (1872). 258). In 

 1887 the matter was fully investigated by Mr. .Arthur Bennett, who fully proved 

 the specific distinctness of the plant, and this view is now generally accepted. 



P. ochreatus belongs to the section of the genus in which the whole of the leaves 

 are submerged, and narrow-linear in shape, the broad floating leaves being entirely 

 absent. It has a wide range in New Zealand, being common in slow-flowing streams 

 and lakes from the North Cape to Otago, in many places forming dense masses. In 

 Australia, according to Mr. Arthur Bennett, it ranges from Queensland to Tasmania ; 

 and Dr. Graebner has lately referred a Japanese plant to the same species. 



Plate 207. Potomojetow ocAreaiws, drawn from specimens collected in the Waikato River. Fig. 1, 

 flower-bud ; 2 and 3, flowers ; 4, back of perianth-segment ; 5, front view of perianth -segment, with 

 stamen; 6, carpels ; 7, a single carpel cut longitudinally ; 8, young fruit ; 9, section of same ; 10, seed. 

 (.4.11 enlarged.) 



