166 “TREUBIA VOL. II, 2—4. 
plants, frequently occurring along the margins of the ponds, were pointed 
out to me as halophytes by Mr. C. A. BACKER, the botanist for the Java Flora: 
the fern Acrostichum aureum L.; the Cyperacea Fimbristylis ferruginea 
VAHL; the Verbenacea Clerodendron inerme GARTNER; the small Composite 
Wedelia biflora D. C.; and the grass Kerinozoma suraboja STEUD.. 
Between the outer ponds of Mr. Görs’s group and the sea, there is 
a belt of mangrove; on the land-side of this belt the ground is often covered 
with the Aizoidea Sesuvium portulacastrum L.. Young sprouts of mangrove 
trees can be seen in great numbers in the ponds themselves, especially in 
their shallow central parts. 
With some effort one may perceive on photo 4 (Plate IX) in the 
middle of the pond two young mangrove sprouts as well as a few shallow 
patches overgrown with Paspalum distichum L.. 
Among the plants occurring with striking frequency in the pond- 
complex of Mr. Görs I may further mention: Pluchea indica LESS.; Crota- 
laria striata D. C.; Acacia farnesiana WILLD.; and Ruellia tuberosa L.. In 
the acacias | very often saw nests of weaver-birds. : 
In the pond-district east of Tandjong Priok the dams between the 
ponds are mostly planted with Rhizophora mucronata LAM., sometimes 
interspersed with Rhizophora conjugata L., as may be seen in photos 8 
and 9 (Plates XIV and XV). 
CHAPTER II. 
The Salinity of the water in the Batavia empangs. 
§ 1. Methods of collecting the data. 
By the salinity of sea-water we generally understand nowadays, follow- 
ing the lead of S.P.L. SORENSEN and MARTIN KNUDSEN, the aggregate 
weight in grammes of all the salts present in. solution in 1000 grammes 
of sea-water, after the bromine and iodine had been first replaced by 
chlorine, the carbonates converted into oxydes and the organic matter 
oxydized. 
The figures given below relative to the salinity of the water in the 
Batavia sea-fish-ponds, were determined by me by means of a series 
of areometers of Dr. R. KüCHLER of IImenau in Thuringia with corres- 
ponding thermometers, and of the hydrographic tables of MARTIN 
KNUDSEN (15). 
It is well known that even with the greatest precautions it must not be 
expected that salinity-determinations, made after this method, should possess 
a higher degree of accuracy than to within 0.1 °/,.. In practice however 
the accuracy is nearly always rather less satisfactory (cf. HELLAND HANSEN (*) ). 
Thus the average error in salinity-determinations by means of areometers, 
