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:-- Odontidium (_hiemale_). -- (_mesodon_). -- _n. sp.,_ same as at Piti on _Conferva._ Denticula (_obtusa_). Navicula. Cymbella, three species. Epithemia. Scarcely any one of these except the _Navicula_ is peculiar to the locality. A fragment apparently of some _Closterium,_ the only one which I have met with in the collection, accompanies one of the specimens.