Whilst He gives me breath, may I praise Him." Nor was this a passing sentiment of his thankfulness for this special favour. We find him, ever and anon, using at the end of any of his descriptions of a new machine which he had perfected, an anagram expressive of his utter dependence on the Divine Being.

I hope that this short statement of the more important of Hooke's mechanical inventions will justify me in the remark with which I began, that Hooke stood very near to Newton. They are twin stars, forming, when casually seen, but one luminary, and that luminary Newton, but when more carefully observed, differing in their brightness "as one star differeth from another star in glory." Had Hooke been born fifty years after Newton, Newton would not have been less. Had he been born fifty years before the great philosopher, Hooke would have been more exalted. Yet was Hooke the forerunner of Newton's glories, the precursor of one who made many crooked things straight.

On the Rare Lichens of Ben Lawers. By HUGH
MACMILLAN, F.R.S.E.

Continued from Vol. III. No. 2, page 268.

Squamaria lanuginosa, Hook. On the rocks in the wood, at the foot of the hill on the east side. This interesting lichen, which is common in shady, subalpine regions in Europe and America, is distinguished by its white pruinose thallus, and by the dense tomentose bluish-black fibres which clothe the under surface of the crenated lobes of the circumference. The apothecia, which are minute, a little elevated above the thallus, of a pale rufous-fuscous colour, and furnished with an inflexed pulverulent thalline margin, very rarely occur. I have frequently gathered specimens of this species in very shady situations, in which the whole thallus was reduced to a leprous byssine mass, not unlike the Lepraria alba of Acharius.

Parmelia fahlunensis, Ach. } Abundant on rocks near

Parmelia stygia, Ach.

the summit; also common on the European and North Ame

rican mountains, extending as far northward as Greenland and Melville Island. These two lichens are too nearly related to each other to be kept distinct; intermediate states very frequently occurring even on the same stone. This view was entertained by Wallroth, Fries, Schaerer, and Meyer. Parmelia ambigua, Ach. Sparingly in rugged hollows and cracks in the bark of pine trees, at the foot of the hill on the east side. It occurs in a fertile state on trunks of trees and dead wood, in the subalpine districts of North America, and on the birch and pine in Sweden and Germany. It has also been found in these countries on rocks, but invariably destitute of fructification. The thallus is usually very imperfect and fragmentary, sometimes only a few segments being present, closely applied to the bark, and sometimes only an aggregation of the soredic warts, constituting almost a mealy crust-like surface. It is generally ochroleucous or greenish straw-coloured; but old specimens frequently occur even on the same tree, of a dull grayish-white colour, to which Fries refers the P. hyperopta of Acharius. I have never seen native specimens in fruit. To me it appears to be merely a tree form of Parmelia conspersa, and Bluff and Fingerhuth were of the same opinion. From P. aleurites, with which Mougeot and Nestler, in their magnificent "Stirpes Cryptogamicæ Vogeso-Rhenana" have confounded it, the farinosesorediferous warts which cover its surface, and the elevated scutellæ sufficiently distinguish it.

Parmelia incurva, Fries. Sparingly distributed over boulders, both at the foot of the hill and at a considerable elevation, generally preferring such as are of quartz formation. It resembles very closely certain states of Squamaria saxicola, or a young plant of Parmelia conspersa, for both of which it has very likely been often mistaken; but the presence of the yellow globuliferous warts with which its surface is almost always thickly covered, as well as its peculiar appressed habit, very narrow multifid laciniæ, recurved at the apices and black and fibrillose on the under side, afford constant distinguishing characters. Perhaps the lichen to which in form and appearance it most nearly approximates, is the Squamaria cæsia,

Hook.; but from that species too the colour of its thallus and apothecia distinguish it. The specimens found at a high elevation on Ben Lawers are of a much darker colour than those found at the foot of the hill, and their segments are generally much broader and more rugose. Several very fine specimens of the normal form occur on boulders by the road side, near Cluny Ferry, about two miles east from Aberfeldy. I have several times gathered the closely-allied Parmelia Mougeotü of Schaerer, on pure white quartz, in the Breadalbane mountains; and I have received very fine specimens from my friend Mr Mudd, found on sandstone rocks, near Cleveland, Yorkshire. Although long known to our lichenists, it has not hitherto received a place in the British Flora as a native of this country.

Solorina crocea, Ach. Abundant along the ridge on the summit. The normal height of this beautiful lichen on the Scottish mountains appears to be 3600 feet, but solitary unfructified specimens occur much lower down on Ben Lawers; and on other mountains of the same elevation, even although forming part of a connected range or chain, it is rare to find a single individual. It seems to prefer micaceous soil in very moist situations; and, for this reason, it is much more common and abundant on the Breadalbane range than on any other mountains in Scotland. On the Swiss Alps it occurs in profusion, from an elevation of 5000 feet; and in Lapland it occurs everywhere in the utmost abundance in the pinewood and exposed fields, but chiefly in a barren state. It extends as far northward as Greenland and Point Lake.

Solorina saccata, Ach. In the damp shady clefts of rocks, in the hollow near the summit. This is a much more common species than the S. crocea, and is not nearly so alpine; isolated specimens occurring in many parts of Scotland, England, and Wales, at a very low elevation. The apothecia also are very different. When first developed, they burst out from beneath the cortical layer of the thallus, and receive a slight, somewhat irregular, border from it; at this stage they bear a great resemblance to those of the S. crocea, but when they become more mature, they sink into the thallus and form

these deep holes or sockets which have given rise to its very appropriate specific name. In Dr Menzies' herbarium, in the Edinburgh Botanic Gardens, a minute and closely-allied species occurs, gathered on the Pacific coast, and named S. orbiculata. In a vertical section of the thallus, we first find a layer of large globose cells, with walls of very irregular thickness; beneath this layer we find another of very dense tissue, composed of smaller polygonal cells, with very thin and transparent walls, in which are developed ovoid grains of a bright green colour, and less solid than those developed in the gonidial layer of Peltidea and Nephroma. These grains are perfectly free in their parent cells, the smallest pressure being sufficient to discharge them. The spores are ellipsoid, bilocular, of a very brown colour, and furnished with a very thick obscurely granulose integument. In germinating, they send out at each of their obtuse extremities, a colourless, very slender filament, which lengthens and ramifies considerably.

Peltidea venosa, Ach. Most abundant on the turfy top of a wall by the road-side, about two miles east from Killin ; and very sparingly in the moist shady clefts of the rocks in the hollow near the summit of Ben Lawers. This lichen is very widely distributed, and occurs in very dissimilar localities; for while it is found occasionally on the summits of the Scottish hills, as well as at a considerable elevation on the mountains of the United States, Canada, Sweden, Lapland, and the higher Alps of Switzerland, its favourite situations appear to be the sides and tops of mossy earth-covered rocks, either in the bed of streamlets, or exposed to the spray of waterfalls; indeed very much the same situations as its congener P. aphthosa affects. In Hooker's Cryptogamia antarctica, the Peltidea venosa is stated to have been found on tufts of moss on the hills of Kerguelen's Land. The specimens observed, however, were stunted and barren, and otherwise in a very unsatisfactory state, presenting, in this respect, a great resemblance to dwarf individuals found on the summits of the Scottish hills, and in the arctic regions, with the difference only of a smoother thallus, and occasional buds on the margin.

Peltidea horizontalis, Ach. Common on moist mossy

rocks at a considerable elevation above Loch-na-Cat. The spores are linear-oblong, attenuated at the two extremities. They are formed of a transparent membrane, everywhere very thin, and their cavity is ordinarily divided into four compartments by three transverse partitions, which it is often difficult to distinguish from the granulose matter with which the whole lamina proligera is filled. They are scattered about the beginning of February on the moist soil, and produce, at each extremity, extremely slender, long, and somewhat branched filaments. This lichen has been found in abundance on wet moss in Kerguelen's Land, and on the summit of the Pic du Midi, one of the peaks of the Pyrenean range, about 9000 feet in height. I may notice here that I observed on the thallus of a specimen of Peltidea canina, gathered near the foot of the hill, that minute and interesting parasite the Scutula Wallrothii, Nob., which appears to the naked eye a mere black point. Tulasne discovered in this plant stylospores, or isolated spores, borne upon short simple stalks, and produced in conceptacles, to which he applied the name of pycnidia. Gyrophora erosa, Ach. On rocks near the summit, Gyrophora cylindrica, Ach. plentiful, and very variable. Gyrophora proboscidea, Ach. Spermogones indicated by

small, very black, elevated spots upon the upper surface of the thallus, and figured by Hedwig as the male parts of fructification, are very common on the three species. Those who wish to investigate this difficult and protean genus thoroughly, should consult Flörke's elaborate Monograph of the Gyrophoræ, or the able paper in the Lichenographia Britannica.

Gyrophora pellita, Ach. On rocks at a low elevation. This is the least alpine species of the genus, occurring on the moorland rocks above Aberfeldy, at a height of from 300 to 400 feet. In this species the trico are frequently transformed into elevated, irregular clusters of much-branched, minute black fibres. Mr Brunton supposes this transformation to take place only after the trica have discharged their spores.

Cetraria sepincola, Ach. On pine trees in the wood at the foot of the hill on the east side, very sparingly, and generally occurring as single isolated individuals.