£78 JOURNAL, BOMBAY NAIUEAL HIST. SOCIETY, Vol. XXVII. 



Aquatic Formation. 



Water is naturally scarce within our region and lias to be collected during the 

 monsoon for irrigation purposes. Wherever possible artificial basins are con- 

 structed, preferably with a rocky bottom, since a sandy or gravelly bottom 

 retains the water only with difficulty. At the time of our visit the amount of 

 water in these tanks was unusually great owing to the exceptionally heavy rains. 

 Just before the rainy season, the smaller ones are generally empty and during 

 ordinary years, the maximun water level must be far lower than that observed 

 by us. 



The chief tanks visited by us are : 



(1) Kailana Lake near Jodhpur (PL V-A.) occupies a comparatively large 

 rocky valley and supphes Jodhpur city with water. The dam is shown in 

 PI. I B., and the luxurious vegetation on the outside forms a striking 

 contrast to that of the surrounding arid hills. The lake itself contains 

 masses of Alg(£, among which various species of Chara were noted. The 

 Naiedacace were represented by Potamogeton crispus and Naias australis. 



There were hardly any semi-aquatic associations along the shores of 

 the lake at the time of our visit, although they probably would be well 

 developed after the partial drying up of the water. Below the dam, 

 however, we found Bergia ammannioides and B. odorata associated with 

 Ammannia baccifera and A. multiflora. 



(2) The tank above the Balsamand Garden near Jodhpur is a small rock basin 

 in which Trapa hispinosa was collected. We have not observed this 

 plant in any other locahty and conclude that it must have been culti- 

 vated here. 



(3) The lake near Mandor (PI. VI-A.) is a large shallow expanse of water 

 in the plain, and is rather difficult of approach on account of its marshy 

 shores. Mandor was our best locahty for Gyperacece and many of these 

 plants occurred in the neighbourhood of the lake. The vegetation on the 

 banks along the muddy irrigation canals leading from the lake is best 

 described as ruderal. The lake as shown on the photograph is probably 

 much larger than in ordinary years. 



(4) A small pond surrounded by marshy ground about 8m. north of Phalodi 

 (PI. XXIV-B.) was filled with muddy water devoid of vegetation, except 

 for a number of immature specimens of Vallisneria spiralis, a plant not 

 observed in any other locahty. The shores were covered by high Gy- 

 peracece partly associating with Andropogon annulatus. The surround- 

 ing damp gravel was a favourite habitat of Bergia odorata. 



(5) The small village tank at Bap has a gravel bottom and partly marshy 

 shores. The submerged association observed by us consisted of Potamo- 

 geton pectinatus, Naias graminea, Naias WelwitscJiH, and Ghara sp. 



(6) Gharsisar Lake outside Jaisalmer town (PI. XII- A.) is not of much 

 interest botanically. 



(7) The same may be said of Amarsagar and Bada Bag tanks, both artificially 

 dammed rock basins (PL XII-B., XI-B.), although the shores may have 

 a rich vegetation in the middle of the dry season. Both irrigate exten- 

 sive gardens. In the Bada Bag (PL XI -A.), a large muddy field of almost 

 pure Ammannia baccifera association was observed. 



(8) A small artificial pond with gravel bottom between Seu and Badka had 

 a flora different from the ordinary type. There was found an association 

 of Nijmplioia lotus and Limnanthemum parvifolium, neither of which was 

 observed elsewhere. We noted also a zone of Ghara sp. 



(9) A few drying-up pools near Barmer railway station were bordered by 

 pure famihes of Eclipta erecta (PL X-A. & B.). Although this plant is 

 ruderal rather than aquatic, it is meetioned here owing to the fact, that 



