THE FLORA OF THE INDIAN DESERT. 



515 



The considerable fossil material collected by us (Mollusca, Brachiopoda 

 Ecnmodermata) has not yet been worked out, but previous determinations 

 admit of no doubt about the Jurassic age of the strata 



Jaisalmer town is built entirely of limestone from these deposits, and there 

 is hardly a house without beautifully carved doors, or window frames or lattices 

 of some sort. The harder varieties of the stone take a fine polish. 



The height of the plateau above the surrounding plain hardly exceeds 100 feet 

 and denudation is very rapid on its margins (see Plate XXX V-A.). Plate VIII- 

 A. gives some idea of the desolate appearance of its surface. Outliers of the 

 plateau are visible in the background of Plate XXXIII-B. 



C. Banner hills. 



These are chiefly of volcanic origin, consisting of Malani rhyohtes, and reach 

 a considerable height. Near Barmer town (Plate XXVI-B.) the lavas are rather 

 porphyritic, and of a brownish colour. Plate XXXVI-B. gives another view of 

 these hills. 



Near the town, at the base of the hills, there is a narrow fringe of sandstones, 

 overlying the lavas, and containing obscure plant fossils and shells. These 

 deposits are of an uncertain age (^). 



The three areas mentioned show distinct differences as regards the floristic 

 composition of their associations. Many species occur only in one or two areas, 

 while some are common to all three, but show striking variations in their numeri- 

 cal relations. 



One of the most characteristic rock plants is Euphorbia neriifolia. This shrub 

 is common in the Jodhpur area, particularly round Kailana lake (Plate V-A.) 

 and on the plateau above Mandor (Plate XXIX- A.). The terraces on the slopes 

 of the above mentioned rocky depression close to the latter place (Plate XXVII- 

 A.) were almost bare except for numerous well developed Euphorbia shrubs. 

 Round Jaisalmer the plant is rare, being only observed near Amarsagar (Plate 

 XIX-A.). It becomes extraordinarily abundant in the Barmer region, where it 

 covers whole hillsides (Plate XXXVII-A, XXXVI-B.) The shrub forms a 

 favourite support for a number of climbing and twining plants, such as Sarco- 

 stemma brevistigma (Plate XXI-A.) and various species of Convolvulus (Plate 

 XXI-B.; the shrub in the centre of the Euphorbia family is Capparis decidua). 

 On Plate XIX-A. the Euphorbia specimens support Ehynchosia mijiima, var. 

 laxifiora ; other plants on this view are Orewia populifolia, Crotalaria burhia, 

 Sida sp., Barleria acanthoides, Aerua tomeniosa, Tephrosia sp., Justicia simplex, 

 Elexisine sp., Aristi a sp. On Kotda hill the plant is , ssociated with the following 

 species: (1) Solanum albicaule (rambling); (2) Capparis decidua ; (3) Ehynchosia 

 minima var. laxifiora (twining); (4) Grewia populifolia, Vernonia cinerascens. 

 Commiphora, Cardiospermum (twining). Asparagus racemosus (climbing); 

 (5) Sahadora oleoides ; (6) Vernonia cinerascens ; (7) Mimosa liamaia. On 

 plate XXXV-B., Euphorbia is shown associating with Barlerit prionilis 

 var. diacantha, Pupalici sp. (rambling), Boerhaavia verticillata (rainblmg), 

 Commiphora. A large shrubbery near Barmer, close to the foot of the 

 hills, consisted of : ^w^p^orfiia neriifolia, Solanum albecaule (rambling), J/jwosa 

 hamata, Boerhaavia verticillata {i&mhlmg), Capparis decidua, Pantcum untidotale, 

 Pupalia sp. (rambling), Vernonia cinerascens, Barleria acannthoides Gymnos- 

 poria montana, Calligonum polygouoides, Achyranthes aspera (rambhng), and 

 one of the Cucurbitaceas (climbing). 



Barleria prionitis var. diacantha (var.nov.) just mentioned as occurring at 

 Barmer was observed in no other locality. Here, however, the plant grew m pro- 

 fusion on the rocky debris of some of he lower hill-slopes sometimes forming 

 pure associations (Plate XXXVII-B.). Barleria hochstetteri, also found at Banner 

 ( on rocks), was observed nowhere else. In the other rocky a reas, the genus was 

 (1) See T. D; LaTouche : Geology of Wedern llajputami-yi-^m. Geol. Surv. 

 of India, Vol, XXXV, Fart I. 



