BOTANY OF FERNANDO NOEONHA. 9 



(Quart. Journ. Geol. Soc. xxviii. p. 33) to the contrary. There 

 are no sedimentary rocks on the island, and granite, the prevailing 

 rock in the neighbourhood of Pernambuco, is entirely absent, while 

 at the same time no basaltic or phonolitic rocks are known from the 

 adjacent mainland*. The "Tertiary conglomerates " of Eattray, 

 showing a former connection with the Tertiary rocks of the 

 adjacent mainland, are quite mythical. In spite of all attempts, 

 it seems quite impossible to fix certainly the period at which the 

 island rose from the bed. of the ocean. That it is of considerable 

 antiquity there is little doubt, however. From the petrological 

 structure of the island it seems certain that it rose from the 

 bottom of the ocean at some remote period, and of course when 

 this happened there was no vegetation upon it. How is the 

 present Flora to be accounted for ? Most of the plants may be 

 relegated to one of three clxisses : — Weeds, or plants introduced 

 intentionally or accideutally by man ; plants of which the seeds 

 or fruits are known to be carried about the ocean by currents ; 

 and plants with eatable fruit which is sought by birds. 



JVeeds. 



To this class belong many of the species. They include all the 

 Malvaceae and nearly all the Leguminosae, the remainder being 

 scattered over other orders. Most of them are plants of world- 

 wide distribution and very common on the adjacent mainland. 

 Few or none occur on the smaller islets, such as Sella Giueta; 

 but where there have been settlements these plants seem to 

 spring up at once. By far the greater number were to be found on 

 the main island in the open central district and in the village. 

 Only one occurred on Sella Griueta, and that was Euxolus viridis. 

 To this section belong all or nearly all the plants with adhesive 

 fruits or seeds, viz.: — Besmodium (4 species), jEscliynomene, 

 Zornia, Plumbago, Boerhaavia (2 species), CJiloris (2 species), 

 Eragrostis ciliaris, Anthephora, Cenchrus (2 species), Setaria 

 scandens. 



The absence of these from the smaller islets seems to show 

 that the bird-fauna is not responsible for their presence here ; 



* When comparing Fernando Noronha with the adjacent continent, it is but 

 just to point out that the nearest point, Cape San Roque, and indeed the whole 

 of the Province of Rio Grande del Norte, is almost entirely unknown as 

 regards its geology and natural history, and that even in the neighbourhood 

 of Pernambuco much remains to be done. 



