INTRODUCTORY CHAPTER. XXxix 



valuable at the present time. It is abundant on the island, and Hildebrandt 

 reported it very common in Somali-land. I did not bring. home sufficient 

 specimens to allow of an experimental trial of this as a material for wood- 

 cuts or other purposes. I learn from Dr Schweinfurth, that he has sent some 

 to Berlin to be tried in this way. 



Many plants are used on the island for the purposes of dyeing — Gaillonia 

 tinctoria, Taverniera sericophylla, Indigo/era tinctoria, Roccella tinctoria. The 

 last-named occurs in abundance, and was formerly exported in great quantity. 

 It is known as shennah. 



Surveying the flora from the point of view of its relations and development, 

 we shall consider the Phanerogams in the first instance ; — and I must state 

 that in making any statistical estimates of the relations of the flora the 

 numbers must be regarded as approximative only. I have already mentioned 

 that the species brought home by the English and German expeditions are but 

 a small part of those that exist in the island. The collections give a fairly 

 representative sample of the flora, and of the more generally distributed plants 

 they contain, I think, a large proportion ; but of the vegetation in the many 

 rocky ravines at high altitudes which sculpture the central granitic region of 

 the island, that from which several of the most interesting of our plants were 

 obtained, we have a comparatively fragmentary gathering. Besides, it has to 

 be remembered that we know comparatively little of the flora of the adjacent 

 mainlands, and that future exploration of these will doubtless necessitate 

 changes in the estimate it is now possible to make. Already an illustration of 

 this is afforded, for since the descriptive part of this flora was printed, the list 

 of plants collected by Mr H. H. Johnston on Kilima Njaro and adjacent parts 

 of tropical Africa has been published, and his discoveries modify in a slight 

 degree the distribution of some of the Socotran forms. Reference to these will 

 be found in the Appendix. 



In the phanerogamic flora the 565 species belong to 314 genera, and are 

 included in 81 orders — giving thus about 7 species to each order and 4 to each 

 genus. Monocotyledones comprise 100 of the total species, or 17 '61 per cent.; 

 the ratio of Monocotyledones to Dicotyledones being therefore as 1 to 4*6. This 

 proportion is about the same as in the Indian Ocean islands. It is largely 

 determined by the number of Graminese and Cyperaceae, which together 

 comprise nearly two-thirds of the Monocotyledones, but the number of 

 Monocotyledones belonging to other groups will, I am confident, be largely 

 increased by future exploration. Both the English and the German expeditions 

 were on the island at the time when few bulbous monocotyledonous plants are 

 in flower, and consequently the occurrence of many species of these is not yet 

 recorded. The gamopetalous species of dicotyledonous plants only exceed the 

 polypetalous by 24 species, which is a small excess for such a flora. 



