324 



NATURE 



[July 31, 1890 



Fernando Noronha. 



Darwin landed on this island on the outward voyage of 

 the Beagle, and collected a few plants, and Moseley suc- 

 ceeded in obtaining specimens of a few plants from the 

 main island and the islet of St. Michael's Mount, but was 

 prevented from making a complete collection in conse- 

 quence of the Challenger being unprovided with the 

 necessary authorization. These plants were described by 

 the writer, and some of them figured in the " Botany of the 

 Challenger Expedition." Provided with funds by the 

 Royal Society, Mr. H. N. Ridley, formerly of the British 

 Museum, and now Government Botanist for the Straits 

 Settlements, visited the island in the summer of 1887, 

 accompanied by Mr. G. A. Ramage and the Rev. T. S. 

 Lea. The party remained on the island, or rather 

 group, for there are several islets besides the main island, 

 forming a chain, which may have formerly been con- 

 tinuous. Thus they had time to explore thoroughly the 

 natural history ; and an account of the botany, by Ridley, 

 has just appeared in the current volume of the Journal of 

 the Linnean Society. The singularly unconnected form 

 of the introductory matter is doubtless due to the hurried 

 manner in which it had to be completed before the 

 author's departure for Singapore. 



Fernando Noronha is in about 3° 50' S. lat., and nearly 

 200 miles from the nearest point of the Brazilian coast. 

 The whole chain is about eight miles in length, and the 

 main island five miles long and nearly two miles across 

 in one part, though very much narrower generally. 



The fragment of the flora published in the " Botany of 

 the Challenger" was considered sufficient to enable us to 

 form an opinion of its general character, and state that 

 there was no peculiarly insular element in the vegetation. 

 This is fully borne out by the subsequent discoveries. 



Mr. Ridley gives no analysis of the composition of the 

 flora beyond classifying the plants as weeds, such plants 

 as might be introduced by sea-currents, and such as have 

 berries and eatable seeds, with examples ; but he does 

 not tabulate the whole. His very brief " summary " 

 follows : — 



" The whole group of islands possesses certain charac- 

 teristics common to all truly oceanic islands and some of 

 those which are merely the relics of vanished continents. 

 In the first place there is the absence of indigenous 

 mammals, and more noticeably of bats, of fresh-water 

 fish, and amphibians. Again, the number of indigenous 

 species, both of plants and animals, is very small, while 

 the number of individuals is very large. The insects are 

 small and dull in colour, and but few of the plants have 

 showy flowers, white and yellow being prevailing colours. 

 A considerable proportion of the indigenous plants are 

 shrubby or arboreous, as in many other oceanic islands ; 

 but arboreous or even shrubby Compositae do not exist, 

 indigenous species of the order being rare in the group." 



There will be differences of opinion, of course, as to the 

 teachings of the data collected by Mr. Ridley and his 

 companions, especially as to whether the present vegeta- 

 tion be a remnant of a former continental flora or a 

 purely derived insular flora of comparatively recent 

 origin. 



Mr. Ridley himself states " that there is no evidence 

 whatever to show a former connection with the mainland 

 of Brazil at any time, in spite of what has been asserted 

 by Dr. Rattray to the contrary." On the other hand, in 

 a sketch of the geology of the island, based on petro- 

 logical notes by Thomas Davies, which follows the 

 enumeration, it is merely doubted " that the evidence is 

 sufficient to prove a connection." 



It appears, too, that " some American petrologists, who 

 have found similar rocks to those of Fernando Noronha 

 in the neighbourhood of Cape San Roque, seem to con- 

 sider that the group may have been connected at one 

 time with the mainland at this point." 



Roughly counting the plants in the enumeration, we 

 NO. 1083, VOL. 42] 



find there are nearly two hundred species of phanero- 

 gams, including weeds and a few others undoubtedly 

 introduced, intentionally or unintentionally, by man. Out 

 of this total, about thirty-two are described as new, or, in 

 about half-a-dozen instances, more fully described than 

 was possible from the imperfect material previously 

 known. So far as present evidence goes, these are all 

 endemic in Fernando Noronha ; but while so much 

 remains to be done in the investigation of the Brazilian 

 flora, it should not be assumed that they are really so. 

 Some of them, indeed, are admittedly very closely allied 

 to previously-described species, and botanists might 

 differ as to the propriety or expediency of treating the 

 majority of them as independent species. And as to the 

 whole, they present no peculiar characteristic suggesting 

 the improbability of their occurring on the mainland. 



The poverty of the flora in species may be largely due 

 to climatal and other conditions. The climate is so dry 

 generally, or the periods of drought are so protracted, 

 that marsh plants, epiphytes, and ferns are almost wholly 

 wanting. Mr. Ridley discovered one ie.rr\, Pellcea geranice- 

 folia, but it was rare and local, and this very widely- 

 spread fern will grow in comparatively dry situations. 



A large number of the plants, including several of the 

 supposed endemic species, bear edible fruits ; yet " there 

 is only one fruit-eating bird on the island, and that is the 

 endemic dove, Zenaida noronha;." This fact tempts Mr. 

 Ridley " to wonder whether the number of endemic 

 species with edible fruit could possibly have all been 

 introduced by this single species of dove, or whether 

 other frugivorous birds may not at times have wandered 

 to the shores." This sentence can hardly convey what 

 Mr. Ridley had in his mind when he wrote ; and being 

 so distant from home he probably had no opportunity of 

 revising it in print. Moreover, it is hardly correct to 

 designate this group of islands as "oceanic." 



Prominent in the vegetation among the assumed new or 

 endemic plants are : Erythrina aurantmca, Cereus insu- 

 laris, Bignonia roseo-alba, Pisonia Darwinii, Sapiian 

 sceleratum, and Ficus noronhce. There are also described 

 two species of Oxalis, three of Ceratosanthes, a genus of 

 Cucurbitaceas, a Sesuvium, a Cuscuta, a Physalis, a 

 Solanum, a Lantana, and three of Cyperus, besides a 

 few others of less familiar genera. Of greater botanical 

 interest is an apparently dioecious Combretacea, pro- 

 visionally placed in Coinbretum as the type of a new 

 section, Terminaliopsis. Taken as a whole, the vegeta- 

 tion is quite that of the mainland deprived of the 

 moisture-loving element. 



In conclusion, it may be stated that the woods men- 

 tioned by the earlier writers have almost disappeared 

 since the main island has been made a convict settlement. 

 W. Botting Hemsley. 



THE BRONTOMETER. 



"pOR more than a century meteorologists have been 

 -*■ puzzled by the exceptional action of the barometer 

 during some (not all) thunderstorms, and during some 

 (but not all) heavy rains. As a general rule, one expects 

 the barometer to fall for rain and bad weather, but in 1784 

 Rosenthal pointed out that "when a thunderstorm ap- 

 proaches the place where a barometer is situated, the 

 mercury in the tube begins to rise ; the nearer the thunder- 

 cloud comes to the zenith of the observer, the higher does 

 the mercury rise, and reaches its highest point when the 

 storm is at the least distance from the observer. As soon, 

 however, as the cloud has passed the zenith, or has become 

 more distant from the observer, the weight of the atmo- 

 sphere begins to decrease and the mercury to fall." 



The recent rapid increase in the number of self-record- 

 ing barometers in use has led to much interest being 

 taken in these fluctuations, which are sometimes very 



