196 TREUBIA VOL. II, 2—4, 
As Spirogyra is very slimy to the touch, which is never the case with 
Chaetomorpha, a tuft of Spirogyra-filaments is to be distinguished at once 
from a corresponding tuft of Chaetomorpha-filaments. 
In conclusion I have to mention that on July 2nd 1918, in a pond 
near Tjilintjing, I found a Characea which was very abundant there. I have 
no record of the salinity of that particular pond; in two ponds in close 
vicinity to the one containing the Characea, the salinity that day however 
‘amounted to 26.5 °/x and 25.3 °/o) respectively. 
In the pond in which the salinity was 26.5 °/oo I also found rather 
important quantities of the little Diatom Gaillionella (Melosira) (Centricae, 
Discoideae). 
When discussing Chaetomorpha I have already had occasion to mention 
how the general luxuriant development of the submerged vegetation in the 
Batavia empangs takes place in the Spring after the conclusion of the 
West-monsoon, or at least after the heavy downpours of rain of a marked 
West-monsoon have fallen. Accordingly the submerged vegetation may 
already have reached its maximum development in April. 
A luxuriant submerged vegetation having once developed in a couple 
of weeks’ time, the situation often remains stationary for a long time. This 
became apparent a. 0. when twice, on April 16th, 1918, and on the 27th of the 
same month, | took a photo from the northern extremity of pond A of 
Map Il (cf. Photo 3, Plate VIII), to get a picture of the submerged vegeta- 
tion existing. there; no difference is to be perceived in the extent and 
distribution of the submerged vegetation as shown in the two photos. 
In the course of the year, and especially towards the autumn the submerged 
vegetation usually begins to decline, which is partly connected with the 
fact that, as we shall see in Chapter V, the submerged vegetation is eaten 
up by the bigger bandeng, and at that very season there is plenty of large 
bandeng in the ponds, which is to be caught and sold at “Pasar Malem” !). 
| furthermore observed how the remains of the old submerged vegetation 
still existing at the end of 1918, sunk away to the bottom of the ponds 
when after the dry East-monsoon of that year the heavy West-monsoon 
rains of the beginning of 1919 set in, which after all, in view of the sudden 
and great variations in the density of the pond-water resulting from great 
masses of rain-water pouring into the ponds, is easily accounted for. 
In the months July till October 1918 Dr. N. H. SWELLENGREBEL also 
collected some data concerning the aquatic plants occurring in the sea- 
fish-ponds of Semarang and Sourabaya. SWELLENGREBEL reports on this 
subject in the “Communications of the Civil Medical Service in the 
Netherlands Indies” (Mededeelingen van den Burgerlijken Geneeskundigen 
Dienst in Nederlandsch-Indié), anno 1919, volume VII (58) and volume X (°!), 
1) “Pasar Malem” (= Night-Market) is a specifically Batavian festival, celebrated 
on the two evenings and nights immediately preceding the Chinese New-Year, This 
latter always falls on or after January 2lst and before or on February 20th. 
