176 THE VICTORIAN NATURALIST. 



in which it is less prominent, may be young females or males, but 

 I have found no white papilla on the base of the last leg, such 

 as exists in the males of P. leuckartii. 



Habitat. — Macedon, Victoria. In and upon rotten wood. 



NOTES ON THE DISTRIBUTION OF AQUATIC 

 PLANTS IN NEW SOUTH WALES. 

 By Rev. W. Woolls, Ph.D., F.L.S., Hon. Member. 

 ( Read before Field Naturalists' Club of Victoria, loth March, 1890.) 

 As some remarks on the distribution of certain aquatic plants in 

 New South Wales may interest Victorian naturalists and induce 

 them to ascertain how far the species extend to both colonies, I 

 take the liberty of referring to such plants of the kind as have 

 come under my own observation. The order which first claims 

 attention is that of Lemnaceae, because the species are but im- 

 perfectly known, and present, as Mr. Bentham observed, some 

 curious organisms for special study. Wolffia arrhiza (Wimm.) 

 which in certain seasons is common on the lagoons of the 

 Hawkesbury, appears like a green globule on the surface of the 

 water, and generally in company with some species of Lejuna. It 

 has not any roots, and the new fronds arise from the side of the 

 older plant. . The fructification is yet unknown, and Baron 

 Mueller, in his review of the Lemnacese (Fragmenta, vol. viii., p. 

 188), is of opinion that the species cannot safely be separated 

 from W. micheli. R. Brown seems to have collected (probably 

 in the Botany swamps) two species of Lemna — Z. trisulca and Z. 

 minor — the former of which occurs less frequently than the latter 

 and is minutely toothed at one end of the frond. Z. minor is 

 still abundant at Botany, especially in stagnant and impure water, 

 and is regarded as a means of purifying the air in marshy places 

 by exhaling oxygen during the night. This plant increases very 

 rapidly by gemmulae, or little buds, and in a short time forms dense 

 masses, so as to conceal the water on which it floats. The fructi- 

 fication of this species is very minute, but, with an ordinary 

 pocket lens, the beautifully reticulated sheath containing the 

 flowers may be clearly seen. I have collected Z. viinot in the 

 neighbourhood of Sydney, and also in ponds at Richmond, and, 

 as far as I can judge, it does not differ from the European species. 

 Z. oligorrhiza (Kurz), as well as Z. fni?ior, occurs in Parramatta, 

 and is distinguished by having more roots, whilst Z. polyrrhiza 

 (Linn.) which is frequent in the lagoons of the Hawkesbury, has a 

 still greater number. It appears to me that the distribution of 

 these little plants is as much influenced by the quality of the 

 water as that of terrestrial plants by the nature of the soil, and it 

 would be interesting to ascertain whether they may not be 

 regarded as affording a test of impurity held in solution. Amongst 



