Darwin, in his correspondence (1859) with Sir Joseph Hooker, refers to the occurrence of large West Indian seeds in the crops of some nestling petrels observed by Sir William Milner at St. Kilda (Life and Letters, II, 147, 148). Mr. Charles Dixon in Ibis (1885) refers to Sir W. Milner’s observation in the case of the Fulmar Petrel (Procellaria glacialis) and speaks of them as Brazilian seeds brought by the Gulf Stream, adding that he himself found a nut in the crop of one of these birds in the same locality. He supposes that the birds pick them up from the water. Mr. Hemsley very kindly wrote to Sir Joseph Hooker recently on this point with the object of obtaining some idea of the nature of the seeds; but after this lapse of time it has not been found possible to satisfy my curiosity. I live in the hope of their proving to be Cæsalpinia seeds.
NOTE 60 (page [202])
Schimper on the Halophilous Character of Littoral Leguminosæ and of Shore Plants generally
As a result of extensive microchemical investigations, this eminent German botanist arrived at the conclusion that plants living on the sea-shore, or in inland stations rich in chlorides, are able, as a rule, to store up in their tissues a large quantity of these salts, a capacity enabling them to live in localities where the subsoil is rich in these materials. This inference, as shown in his experiments, is just as applicable to the shore-plants of temperate regions, such as Aster tripolium, Crambe maritima, and Eryngium maritimum, as it is to such typical littoral plants of the tropics as Barringtonia speciosa, Ipomœa pes capræ, Scævola Koenigii, Tournefortia argentea, &c. However, with the Leguminosæ experimented upon, this capacity of storing up chlorides was often exhibited but slightly or not at all; and characteristic Pacific beach-plants, such as Canavalia turgida, Pongamia glabra, and Sophora tomentosa are especially cited as examples (Schimper’s Ind. Mal. Strand-flora, pp. 140-151; Wolff’s ash-analyses are here quoted).
NOTE 61 (page [215])
Meteorological Observations on the Summit of Mauna Loa
The summit is formed of bare rock and sand, the phanerogamic vegetation ceasing a couple of thousand feet below. Some low plant-forms doubtless occur under the moist, warm conditions near the steam-cracks, since Wilkes mentions his finding a small moss; but with this exception the surface may be described as sterile.
Dryness of the Air and Electrical Phenomena.—Wilkes refers to the association of these conditions more than once in his narrative. Whenever, as sometimes happened, the dew point could not be obtained with Pouillet’s hygrometer, electricity was easily excited, and was developed in large sparks. On taking off the clothes at night, sparks would appear. As shown in the table subjoined, electrical phenomena were noticed during the first few days of my sojourn on the summit when the relative humidity was very low. My red blanket at night crackled in my hands and emitted sparks, and a glowing line was produced by drawing the finger along. Whilst the air was in this condition I observed that the wings of dead butterflies lying on the ground stuck to my fingers tenaciously like a needle to a magnet. The adhesiveness disappeared when the excessive dryness gave place to humidity. The physiological effect on me of the associated dryness and electrical state of the air was displayed in a hot, dry, sweatless skin (cracking and chapping rapidly), severe headache and sore-throat, general lassitude, and great irritability. When the weather changed and the air became humid, these unpleasant symptoms quickly disappeared.
As a result of these dry conditions on the summit of Mauna Loa, decomposition does not occur. I found in one place on the top, on the site of an old camp, the remains of a quarter of beef, the meat fresh but dried up. From a water-bottle left behind by one of the party and subsequently restored to him, I learned that the visit had been made in the previous summer. This non-decomposition seems a little strange, since, as remarked below, flies and other insects were not infrequent on the summit. However, as Hann remarks, when speaking of mountain climates, everything dries much more quickly at great altitudes; animals that have been shot, or killed by falling, become mummies without undergoing decay (Schimper’s Plant-Geography, 697).... The scorching power of the sun in a sky usually cloudless, or nearly so, was a trying feature of my daily experiences; and I found that when I faced it with unshaded eyes during my walks I suffered from severe pain in the eyeballs at night.
Insects on the Summit.—It may seem a strange thing to relate, that in a region apparently absolutely sterile, the flies and other winged insects caused me much discomfort in my small tent when I was confined to it through illness. When lying down one morning I noticed the house-fly, the blue-bottle, and two or three other flies, small beetles not over a fifth of an inch in size, a moth, and a wasp. They were no doubt quite happy in the heat, as the temperature inside was over 80° F., and the sun’s rays felt almost scorching through the thin duck canvas. Butterflies (and occasionally large moths) were often observed flying in a drowsy condition about the summit and were easily caught. They were fond of fluttering around the steam-holes. In places, numbers were to be seen dead and dried up on the ground, the detached wings lying about. In the case of a recently dead butterfly I found its carcase already attacked by numerous small bugs. The butterflies were most frequent when there was a fresh southerly breeze, and were doubtless blown up the slopes from the forests below.
Whymper in his Travels amongst the Great Andes of the Equator gives many particulars of the occurrence of insects at great elevations. He noticed beetles, diptera, butterflies, moths, and several other insects at altitudes of 15,000 to 16,000 feet. At 16,500 feet he obtained a small bug of the genus Emesa. He quotes Humboldt and Bonpland as showing that insects are transported into the upper regions of the atmosphere 16,000 to 19,000 feet above the sea, and he remarks that the transportation of insects by ascending currents of air has occasionally been observed in operation. These facts bear directly on the dispersal of insects.
The Winds.—My tent, which was pitched near the middle of the western border of the crater, happened to be situated in the battle-ground of the northerly and southerly winds, in a region of gusty winds, fitful airs, and dead calms. The northerly winds were usually from N.-N.N.W. and the southerly winds from S.W.-S.S.W., easting in either case being rarely observed, the northerly winds rather prevailing at night. As a result of this location miniature whirlwinds were frequent in the vicinity of my tent, which carried sand into the air and more than once threatened to lift up my tent bodily and carry it off into the crater below. At the north end of the crater-border north-easterly winds prevailed, and at the south end southerly winds occasionally showing easting. When on one occasion I walked round the crater-margin, a fresh south-easterly wind prevailed at most parts of the circumference except in the vicinity of my camp, where there was a light S.S.W. wind both at 8 a.m. and 6 p.m. when I started and returned. The local character of the winds was often displayed in my walks. On one occasion, having left my camp, where a southerly wind was blowing, and walked half a mile to the north, I found a bitterly cold N.N.E. gale in my face which so impeded my progress that I returned to my camp where the same southerly breeze continued.