Chbeseman. — Contributions to Knowledge of Flora of N.Z. 9 



present it is in small quantity ; but it should be kept under observation 

 and not allowed to spread. It is well known that its introduction into 

 Florida resulted in the blocking of steamer navigation in several slow- 

 running rivers. 



Hydrocleis nymphaeoides Buchen. 



I am indebted to Mr. Neve for numerous specimens of this handsome 

 water-plant, which he informs me is now plentiful in several lagoons or 

 backwaters near the Thames Kiver, at Te Aroha, and is apparently rapidly 

 increasing. According to inquiries kindly made for me by Mr. Neve, it was 

 planted nearly twenty years ago by a Mr. Wood in a lagoon on his property 

 about a mile and a half from Te Aroha. In this locality it now covers an 

 area of more than an acre in extent, and has become a considerable nuis- 

 ance, blocking up drains and water-channels. The beauty of the flowers 

 has induced several settlers to transfer it to other localities near Te Aroha. 

 In all of these it is rapidly increasing, and there is every probability of its 

 spread in suitable places in the Thames Valley. It is a common plant in 

 South America, ranging from Venezuela to Buenos Ayres, and is now widely 

 cultivated in gardens. 



Polypogon fugax Nees. 



This has spread very rapidly in the Auckland Provincial District, and is 

 now common in most districts in brackish-water swamps. 



Art. II. — The Age and Groivth of the Kauri (Agathis australis). 



By T. F. Cheeseman, F.L.S., F.Z.S., Curator of the Auckland Museum. 



[Read before the Auckland Institute, 3rd December, 1913.] 



There is a well-known tendency in human nature to exaggerate that which 

 is really large, and, consciously or unconsciously, to make it appear even 

 larger and more important than it really is. Even in such a matter as the 

 height of the taller trees, their girth, and still more their estimated age, is 

 this peculiarity evident. Take, for instance, the statements that have been 

 made respecting the Dragon-tree of Orotava, in the Canary Islands. This 

 celebrated tree, which was destroyed by a storm in 1851, had a diameter 

 of over 26 ft., and was estimated by some early travellers to have an age 

 of from eight thousand to ten thousand years. Later on these figures were 

 reduced to five thousand or six thousand, and at the present time good 

 authorities consider this estimate far too high. So also with respect to the 

 well-known baobab (Adansonia digitata), which Humboldt speaks of as 

 ' being the oldest organic monument of our planet." In 1750 the French 

 traveller Adanson calculated the age of a specimen observed at Senegal to 

 be over five thousand years. Nowadays it is universally believed that this 

 record is far too high, and was probably based more on vague conjecture 

 than on actual measurement. Coming down to recent times, the immense 

 size of the " big trees " of California (Sequoia gigantea) led to conjectures 

 as to their age varying from three thousand to six thousand years. But 

 when Professor Whitney, the State Geologist of California, took the first 

 accurate measurements it was proved that a tree 24 ft. in diameter con- 



