The Algae from lower localities are but few in number, and some of these of very common forms. We have for instance from the Ganges, opposite Bijnour, a Batrachospermum and Conferva crispata, the former purple below, with specimens of Chantransia, exactly as they might occur in the Thames. The Conferva, or more properly Cladophora, which occurs also under various forms, at higher elevations, as in the neighbourhood of Simla and Iskardo, swarms with little parasites, but of common or uninteresting species. In the Bijnour specimens, these consist of common forms of Synedra, Meridion circulare, and a Cymbella, on others from Dacca, there are about three species of Synedra,* {Two of these appear to be S. Vaucheriae and S. inaequalis.] a minute Navicula and Gomphonema curvatum. Nothing, in fact, can well be more European. One splendid Alga, however, occurs at Fitcoree, in Behar, on the banks of nullahs, which are dry in hot weather, forming a purple fleece of coarse woolly hairs, which are singularly compressed, and of extreme beauty under the microscope, from the crystalline green of the articulated string which threads the bright red investing sheath. This curious Alga calls to mind in its colouring Caenocoleus Smithii, figured in English Botany, t. 2940, but it has not the common sheath of that Alga, and is on a far larger scale. One or two other allied forms, or species, occur in East Nepal, to which I purpose giving, together with the Behar plant, the generic name of Erythronema. From the Soane River, also, is an interesting Alga, belonging to the curious genus Thwaitesia, in which the division of the endochrome in the fertile cells into four distinct masses, sometimes entirely free, is beautifully marked. In some cases, indeed, instead of the ordinary spores, the whole moss is broken up into numerous bodies, as in the fertile joints of Ulothrix, and probably, as in that case, the resultant corpuscles are endowed with active motion. In Silhet, again, is a magnificent Zygnema, allied to Z. nitidum, with large oval spores, about 1/285 part of an inch long, and a dark golden brown colour, and containing a spiral green endochrome.
Leaving, however, the lower parts of India, I shall first take the species which occur in Khasia, Sikkim, Eastern Nepal, and the adjoining parts of Tibet.
In the hot valleys of the Gtreat Rungeet, at an elevation of about 2000 feet, we have the Erythronema, but under a slightly different form; at Nunklow, at about the same height; in Khasia, again, at twice that elevation; in Eastern Nepal, at 12,000; and, finally, at Momay, reaching up to 16,000 feet. In water, highly impregnated with oxide of iron, at 4000 feet in Sikkim, a Leptothrix occurred in great abundance, coloured with the oxide, exactly as is the case with Algae which grow in iron springs in Europe. At elevations between 5000 and 7000 feet, several European forms occur, consisting of Ulothrix, Zygnema, Oscillatoria, Lyngbya, Sphaerozyga, Scytonema, Conferva, and Cladophora. The species may indeed not be identical with European species, but they are all more or less closely allied to well-known Hydrophytes. One very interesting form, however, either belonging to the genus Zygnema, or possibly constituting a distinct genus, occurs in streams at 5000 feet in Sikkim, consisting of highly gelatinous threads of the normal structure of the Zygnema, but forming a reticulated mass. The threads adhere to each other laterally, containing only a single spiral endochrome, and the articulations are very long. Amongst the threads are mixed those of some species of Tyndaridea. There is also a curious Hormosiphon, at a height of 7000 feet; forming anastomosing gelatinous masses. A fine new species of Lyngbya extends up as high as 11,000 feet. At 13,000 feet occurs either some simple Conferva or Zygnema, it is doubtful which from the condition of the specimens; and at the same elevation, in the nearly dry bed of the stream which flows from the larger lake at Momay, amongst flat cakes, consisting of felspathic silt from the glaciers above, and the debris of Algae, and abounding in Diatomaceae, some threads of a Zygnema. At 17,000 feet, an Oscillatoria, attached or adherent to Zannichellia; and, finally, on the bare ground, at 18,000 feet, on the Donkia mountains, an obscure species of Caenocoleus. On the surface of the glaciers at Kinchinjhow, on silt, there is a curious Palmella, apparently quite distinct from any European form.
Amongst the greater part of the Algae, from 4000 feet to 18,000 feet, various Diatomaceae occur, which will be best noticed in a tabular form, as follows; the specific name, within brackets, merely indicating the species to which they bear most resemblance:—
Himantidium (Soleirolii) 4000 to 7000 ft. Sikkim
Odontidium (hiemale, forma minor) 5000 to 7000 ft. Sikkim
Epithemia, n. sp. 7000 ft. Sikkim
Cymbella — Sikkim
Navicula, n. sp. — Sikkim
Tabillaria (flocculosa) 6000 to 7000 ft. Sikkim
Odontidium (hiemale) 11,000 ft. Sikkim
Himantidium 16,000 ft. Momay
Odontidium (turgidulum) 17,000 ft. Momay
Epithemia (ocellata) — Tibet
Fragillaria 18,000 ft. Momay
Odontidium (turgidulum) — Momay
Dictyocha (gracilis) — Momay
Odontidium (hiemale) — Kinchinjhow
We now turn to those portions of Tibet or the neighbouring regions, explored by Dr. Thomson and Captain Strachey. The principal feature in the Algology is the great prevalence of species of Zygnema and Tyndaridea, which occur under a variety of forms, sometimes with very thick gelatinous coats. In not a single instance, however, is there the slightest tendency to produce fructification. Conferva crispata again, as mentioned above, occurs in several localities; and in one locality a beautiful unbranched Conferva, with torulose articulations. At Iskardo, Dr. Thomson gathered a very gelatinous species of Draparnaldia, or more properly, a Stygeoclonium, if we may judge from a little conglomeration of cells which appeared amongst the threads. A Tetraspora in Piti, an obscure Tolypothrix, and one or two Oscillatoriae, remarkable for their interrupted mode of growth, complete the list of Algae, with the exception of one, to be mentioned presently; as also of Diatomaceae, and of the species of Nostoc and Hormosiphon, which occurred in great profusion, and under several forms, sometimes attaining a very large size (several inches across), especially in the districts of Le and Piti, and where the soil or waters were impregnated with saline matters. It is well known that some species of Nostoc form an article of food in China, and one was used for that purpose in a late Arctic expedition, as reported by Dr. Sutherland; but it does not seem that any use is made of them in Tibet, though probably all the large species would form tolerable articles of food, and certainly, from their chemical composition, prove very nutritious. One species is mentioned by Dr. Thomson as floating, without any attachment, in the shallow water of the pools scattered over the plains, on the Parang River, separated only by a ridge of mountains from Piti, broad and foliaceous, and scarcely different from the common Nostoc, which occurs in all parts of the globe. I must not, however, neglect to record a very singular new genus, in which the young threads have the characters of Tyndaridea, but, after a time, little swellings occur on their sides, in which a distinct endochrome is formed, extending backwards into the parent endochrome, separated from it by a well defined membrane, and producing, either by repeated pullulation, a compound mass like that of Calothrix, or simply giving rise to a forked thread. In the latter case, however, there is no external swelling, but a lateral endochrome is formed, which, as it grows, makes its way through an aperture, whose sides are regularly inflected. I have given to this curious production the name of Cladozygia Thomsoni.
The whole of the above Algae occurred at heights varying from 10,000 to 15,500 feet. As in the Southern Himalayan Algae, the specimens were infested with many Diatomaceae, amongst which the moat conspicuous were various Cymbellae and _Epithemiae. The following is a list of the species observed.
Cymbella (gastroides).
— (gracilis).
— (Ehrenbergii)
and three others.
Odontidium (hiemale).
— (mesodon).
— n. sp.
Epithemia n. sp.
Synedra (arcus).
— (tenuis).
— (aequalis).
Denticula (obtusa).
Gomphonema (abbreviatum).
Meridion circulare.
There is very little identity between this list and that before given from the Southern Himalayas, as is the case also with the other Algae. Till the species, however, have been more completely studied, a very accurate comparison cannot be made.
In both instances the species which grow in hot springs have been reserved in order to make their comparison more easy. I shall begin in an inverse order, with those of the springs of Pugha in Tibet, which attain a temperature of 174 degrees. Two Confervae only occur in the specimens which have been preserved, viz., an Oscillatoria allied to that which I have called O. interrupta, and a true Conferva extremely delicate with very long articulations, singularly swollen at the commissures. The Diatomaceae are:—