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