INSULAR FLORAS. 469 



species of about the same dimensions. The last I have 

 to mention individually are Dracczna Cinnabari and Aloe 

 Perryi, two of the most interesting plants of the island, 

 belonging to types equally prominent in the Canary Islands. 

 These plants yield the Socotran "Dragon's Blood" and 

 "Aloes" respectively; yet, although these products have 

 been articles of commerce for centuries, the trees that 

 yielded them were unknown botanically. 



Although the flora of Socotra is still very imperfectly 

 known — perhaps not more than half known as to number 

 of species — nearly 600 species of flowering plants have 

 been collected, and after making a considerable deduction 

 for introductions there remain some 500 indigenous species, 

 upwards of 200 of which are endemic, or at least have not 

 hitherto been found out of the island. The total of species 

 given above represent 314 genera, and 81 natural orders. 

 There are 20 endemic genera, 18 of which are monotypic ; 

 and of the genera having a wider range 136 are represented 

 by endemic species, and 98 by endemic species only. 

 Such are the principal statistics of the flora, so far as they 

 are ac present known. The proportions of the various 

 groups and subdivisions offer no special anomalies. About 

 seven species to each order and four to each genus is rather 

 low, but future explorations will undoubtedly raise these 

 numbers ; and also, probably, as Dr. Balfour suggests, alter 

 the ratio of monocotyledons to dicotyledons, because both 

 the English and German expeditions botanized at a season 

 when few bulbous plants are in flower. As it is they com- 

 pose 100 out of 565 flowering plants, or 17*6 per cent, 

 which is low for a tropical region, though not for a tem- 

 perate one. 



Dr. Balfour has tabulated and analysed the constituents 

 of the Socotran flora in a most elaborate manner, so that it 

 is possible to follow its relationships generally and the 

 affinities of the endemic forms. Altogether the relationships 

 are much more strongly African than Asian ; yet it is also 

 evident that South Arabia forms part of a flora common to 

 Socotra and Abyssinia, with wider western and southern 

 extensions than eastern. But there are some specially 



