FLOKULA ADENENSIS. V 



valleys. Prom these materials the present Elorula has been 

 compiled. 



Most of the plants have required a careful comparison with a 

 large suite of specimens from various localities, and the consulta- 

 tion of a formidable array of works on Indian and Arabian botany, 

 in order to determine their synonymy and geographical distri- 

 bution. 



These labours have been greatly lightened by daily reference to 

 Sir William Hooker's unrivalled herbarium and rich library ; of 

 both of which I have been permitted to make unrestricted use. 

 Without repeated examinations of the East Indian Herbarium, 

 and of the Arabian, Abyssinian, and Egyptian collections of Sieber, 

 Delile, Aucher-Eloy, Schimper, and other travellers, in all of 

 which the Kew Herbarium is peculiarly rich, the work could not 

 have been accomplished. To Dr. Hooker I am indebted for hourly 

 advice and assistance ; while his entire Aden collections have been 

 placed at my disposal for examination and description. Without 

 this privilege the Elorula could not have been commenced, as his 

 collections considerably exceeded my own in number of species, 

 and they thus form the basis of the Mora. To Gr. Bentham, Esq. 

 I have to acknowledge my obligations for assistance in the deter- 

 mination of several specimens of Leguminosa, Scrophularinece, and 

 Lavandula ; as well as for the free use of his Herbarium. 



Before proceeding to the purely descriptive matter, it appears 

 desirable to notice, 1st, the physical aspect and climate of Aden ; 

 2nd, a few of the peculiarities of its flora ; 3rd, some facts in the 

 geographical distribution of the species ; and finally, to institute a 

 comparison between its flora and those of one or two similarly 

 situated localities. 



1. Aden is a small rocky peninsula, in many features resembling 

 our other stronghold, Gibraltar ; and is situated on the southern 

 coast of Arabia, in 12° 47' N. lat., and 45° 10' E. long. The 

 maritime region called Tehama, of which it is a promontory, is a 

 sandy, barren tract from 20 to 100 miles in breadth, extending along 

 the shore of the Red Sea, from a point a little east of Aden to the 

 G-ulf of Akaba. A mountainous region of 4-7000 feet in eleva- 

 tion rises immediately beyond ; this, from its height, attracts a con- 

 siderable portion of the moisture borne from the Indian Ocean by 

 the north-west monsoon, and thus, enjoying a climate favourable 

 to the growth of luxuriant cereals and fruits, it has for ages been 

 called the Happy Arabia. It forms a striking contrast to the 

 sterile Tehama, in the southern portion of which rain but rarely 



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