350 Transactions. — Botany. 



Abt. XXIX. — On the Occurrence of Ottelia in Neiv Zealand. 

 By T. F. Cheeseman, F.L.S., F.Z.S. 



[Read before the Aicckland Institute, 10th October, 1898.] 



Rather more than a year ago I had occasion to visit the 

 three httle volcanic hills at Ihumatao, which unite to form 

 the promontory jutting out into the Manukau Harbour to the 

 south of Weekes Island. Taking a short cut from one of 

 these hills to regain the road to Mangare and Onehunga, my 

 attention was attracted by the large yellowish-white flowers 

 of a water-plant which quite covered the surface of a small 

 pond, and which was evidently a stranger to me. On ex- 

 amination it proved to be Ottelia ovalifolia, a species which is 

 not uncommon on the eastern side of Australia, ranging from 

 Victoria to the North of Queensland, but which had not been 

 previously noticed in New Zealand. Curiously enough, it 

 belongs to the same order — Hydrocharidacece — as Vallisneria 

 spiralis, which a few years ago appeared in Lake Takapuna, 

 and has since become extremely iDlentiful there (see Trans. 

 N.Z. Inst., 1896, p. 386). Ottelia, however, is very dissimilar 

 in appearance to Vallisneria. The leaves, which are numerous 

 and densely tufted, are borne on stout cylindrical petioles, 

 varying in length in accordance with the depth of the water. 

 These petioles are greatly swollen at the base, forming a mass 

 of air-cells. The blade of the leaf is about oval in shape, and 

 from 2 in. to 3 in. in length, and lies flat on the surface of the 

 water. The flower-stalks rise just above the surface of the 

 water, each one bearing a single rather large yellowish-white 

 flower. The flowers are produced in profusion during the 

 whole of the summer months, giving the plant a very at- 

 tractive appearance. 



No doubt Ottelia has been introduced from Australia, but 

 whether purposely or by accident I am unable to say. The 

 locality is a remarkable one for a naturalised plant to make 

 its first appearance, and the few settlers residing in the 

 vicinity have no information to give as to its establishment, 

 beyond the fact that it has existed in the pond for many 

 years past. So far as I am aware, the plant has never been 

 in cultivation in Auckland, either in private gardens or in 

 nurseries. It is certainly not usually cultivated in Australia, 

 and its name does not appear in any of the nurserymen's lists. 

 As the pond is an isolated one, the plant is not likely to spread 

 further ; but if by chance it should be conveyed to any of the 



