CI. XII. PLANT HISTORY. 315 



indication throughout our journey of regular compliance 

 with the injunctions for daily prayer, so strictly observed 

 in most Mohammedan countries. 



After resuming our route we soon found evidence that 

 we were entering upon a new botanical region — that of 

 the Atlantic coast. Besides numerous species not seen 

 since we had left Mogador at the end of April, we here 

 found for the iirst time several conspicuous plants cha- 

 racteristic of this region. In hedges, and among bushes, 

 a tall Bupleurum, (B. canescens of Schousboe) grew to a 

 height of eight or ten feet, and in similar situations 

 Periploca Icevigata was just forming its fruit. 



The facts known as to the distribution of the last- 

 named plant, and the allied species, Periploca grceoa, 

 suggest speculations as to their past history that deserve 

 some passing notice. The genus Periploca, which takes 

 its name from the twining stems of the species first known 

 to botanists, has its centre in the sub-tropical zone of the 

 Asiatic continent. The single mainly western species is 

 Periploca Icevigata. This appears to be common in the 

 Canary Islands, and grows freely in the tract now visited 

 by us to the north-west of Mogador. It has been found 

 in abundance on some rocky islands near the coast ot 

 Sicily ; but, in spite of the silky hairs attached to the 

 seeds, it has not spread itself to neighbouring islands, nor 

 to the Sicilian coast. It has been detected in two or three 

 places in the south-east of Spain, and here and there in 

 rocky places on the skirts of the desert in the interior of 

 Algeria and Tunis. Finally, it was long ago found by 

 Labillardiere in one place on the coast of Syria. All this 

 points to the former wide diffusion of a plant which no 

 longer finds favourable conditions of existence, unless, 

 perhaps, in the Canary Islands. Its presence in the 

 interior of North Africa may possibly date from the period 

 when it grew near the coast of a great gulf opening to the 

 Atlantic ; but it is not easy to understand how it has held 

 its ground in a climate so different from that of its 



