Plate 206.— POTAMOGETOX CHEESEMANII. 



Family NAIAD ACE^.] [Genus POTAMOGETON, Linn. 



Potamogeton Cheesemanii, A. Bennett in Journ. Hot. xxi (1883), 66; Ckeesem. Man. N.Z. Fl. 749. 



Allan Ciiniiingham was the first to collect this species in New Zealand, for 

 although he referred his specimens to the widespread P. natans, the description of 

 the leaves given in the " Precursor," where he says " foliis natantibus petiolatis 

 ellipticis basi apiceque rotundatis," agrees with P. Cheesemanii, and does not suit 

 P. natans, which has acute or subacute leaves, often more or less subcordate at the 

 base. His specimens were gathered " in stagnant waters near the missionary station 

 on the Kenkeri River, Bay of Islands." It was also gathered in early times by 

 Mr. Colenso and Dr. Sinclair, and probably by other botanists ; but as Sir J. D. 

 Hooker, both in the - Flora" and the " Handbook," confused the species with P. natans, 

 it IS difficult to be sure of the identity of the specimens he had before him. Its 

 specific distinctness was first pointed out by Mr. Arthur Bennett, of Croydon, in the 

 Journal of Botany for 1883 (p. 66). his description being based on specimens collected 

 by myself m St. John's Lake, near Auckland. It is now known to be by far the 

 most abundant member of the genus found in New Zealand, ranging from the North 

 Cape to Stewart Island, and from sea-level to quite 4,000 ft. altitude. 



P. Cheesemanii. in addition to the shape of its floating leaves, can be at once 

 distmguished from P. natans by possessing numerous well-developed submerged 

 leaves, which are much longer and proportionately much narrower than the floating 

 leaves, and which gradually pass into them towards the upper part of the stem. 

 In P. natans the submerged leaves are often absent, and if present are very narrow- 

 linear and semi-terete, sometimes almost setaceous. According to Mr. Bennett 

 {Journal of Botany, 1887, p. 177), P. Cheesemanii occurs in Tasmania as well as New 

 Zealand. 



In the last revision of the genus— that of Dr. Graebner, published in heft 31 

 of the " Pflanzenreich "—eighty-seven species are accepted. Of these, five are 

 found in New Zealand, three of them (P. natans, P. polygonifolius, and P. pectinatus) 

 being practically cosmopoHtan. The remaining two extend to the Australian 

 Continent. 



Plate 206,^ Polaimgeton Cheesemanii, drawn from specimens collected on the Waikato River. 

 Fig. 1, flower ; 2 and 3, front and back view of anther, with perianth-segment ; 4, caqjels ; .5. section 

 of a carpel ; 6, ripe carpels ; 7, a single carpel separated from the rest ; 8, section of ripe' carpel • 

 9, seed. (All enlarged.) ' 



