It is not my intention in the present appendix to give specific characters or even accurately determined specific names to the different objects within its scope, which have come under investigation, as collected by Dr. Hooker and Dr. Thomson. To do so would require far more time than I have at present been able to devote to the subject, for though every species has been examined microscopically, either by myself or Mr. Broome, and working sketches secured at the same time, the specific determination of fresh water Algae from Herbarium specimens is a matter which requires a very long and accurate comparison of samples from every available locality, and in the case of such genera as _Zygnema, Tyndaridea,_ and _Conferva,_ is, after all, not a very satisfactory process. The object in view is merely to give some general notion of the forms which presented themselves in the vast districts visited by the above-mentioned botanists, comprising localities of the greatest possible difference as regards both temperature and elevation; but more especially in the hot-springs which occur in two distant parts of the Himalayas and in Behar, and these again under very different degrees of elevation and of extrinsic temperature. 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