Imágenes de páginas
PDF
EPUB

memoirs and treatises on important subjects of investigation, and to offer pecuniary encouragement to men of talent and attainment to engage in scientific research. It is believed that no institution in the country effects either of these objects to any great extent. The nearest approach to it is the practice of the Academy, and other philosophical societies, of publishing the memoirs adopted by them. These, however, can rarely be works of great compass. No systematic plan of compensation for the preparation of works of scientific research is known by the committee to have been attempted in this or any other country. It can scarcely be doubted that an important impulse would be given by the Institution, in this way, to the cultivation of scientific pursuits; while the extensive and widely ramified system of distribution and exchange, by which the publications are to be distributed throughout the United States and the world, would secure them a circulation which works of science could scarcely attain in any other way.

"It is an obvious characteristic of this mode of applying the funds of the Institution, that its influence would operate most widely throughout the country; that locality would be of comparatively little importance as far as this influence is concerned; and that the Union would become, so to say, in this respect, a great school of mutual instruction.

"The committee' would remark, in conclusion, that, in a plan of operations of this kind, very much depends upon the activity and intelligence with which it is administered. The character of the Board of Regents is a sufficient warrant for the prudence and good judgment which will watch over the general interests of the foundation; while the reputation of the Secretary and his assistant, the Librarian, is so well established in their respective departments, as to render any tribute from the committee entirely superfluous. "All which is respectfully submitted by the committee.

"December 4th, 1847."

EDWARD EVERETT, (Chairman,)
JARED SPARKS,

BENJAMIN PEIRCE,

HENRY W. LONGFELLOW,
ASA GRAY.

NOTE."Professor Agassiz was named of the committee, but, owing to his absence at the South, was unable to take part in the preparation of this report."

Mr. Tuckerman communicated the following arrangement and description of the Lichenes of the northern portion of North America, viz.:

A Synopsis of the Lichenes of the Northern United States and British America, by EDWARD TUCKErman.

LICHENES.

Perennial, aerial Algæ, vegetating only under the influence of moisture, which is imbibed by the whole surface, propagated by spores (sporidia), and also by the cells (gonidia) of the green layer.

Thallus (universal receptacle, Ach.) composed of three layers, viz.: the cortical, the medullary, and the gonimous; evolved from a hypothallus (the elementary state in which the layers are confused, and discernible afterwards as cylindrical cells, and also as fibres on the under side of foliaceous Lichenes, and forming the base, closely adnate to the matrix, in crustaceous ones), typically horizontal or vertical. The horizontal thallus is either crustaceous (often somewhat lobed at the circumference or squamulose), or foliaceous (becoming sometimes in degenerate states crustaceous). The vertical thallus is either compressed (subfoliaceous), or terete (fruticulose); of both of which the filamentous thallus and the pendulous thallus are degenerations. In Cladonia and Stereocaulon a vertical thallus (podetium) arises from the primary horizontal thallus, and is itself often besprinkled with a kind of secondary horizontal thallus in the form of leaf-like scales. Lichenes are reproduced in two ways; 1. by gonidia, the (normally green) cells of the green (gonimous) layer, which appear on the surface as irregularly shaped powdery masses (soredia), and propagate either on the original thallus, forming foliaceous or squamulose

* This enumeration, originally prepared for Dr. Gray's Manual of the Botany of the Northern States, has been enlarged by the addition of many species from Arctic Anierica, and from the Pacific coast, and is now published in the hope that it may open the way to a more complete and satisfactory account hereafter. The system is that of Fries, as presented in his Lichenographia Europœa Reformata, with some emendations derived from his later works. The characters of the sections and genera in the Lichenographia have been throughout the basis of those here given, and in part are adopted entire. In the citation of authorities for specific names, the common usage has been followed; but the writer has elsewhere adopted what appears the preferable one (Enum. Lich. N. Amer. 1845), where will also be found some account of the Friesian System.

expansions, or external to the original thallus, forming new individuals of the parent thallus; and 2. by sporidia, consisting of subglobose or elliptical cells, which are either naked or contained in other elongated more or less vertical cells (asci), and immersed in the thalamium (or fructification proper), and propagate new individuals of the species. The thalamium is either rounded, gelatinouswaxy, and the asci converging (nucleiform); or flattened at length into a rigid, persistent, or afterwards collapsing lamina (subdisciform); or originally disciform (open); and is itself contained in a receptacle (exciple), either of the same color with and like the thallus (thalline exciple), or of different color and nature (proper exciple). The whole fructification constitutes the apothecium, which is typically round, though also occurring normally oblong and linear (lirellaform), and is either excavated with a contracted margin (urceolate); or slightly concave with an elevated margin (scutelliform); or very concave-scutelliform (cyathiform); or very concave-scutelliform and pervious (infundibuliform, a term applied also to the pervious cup-bearing podetia of Cladoniæ); or goblet-shaped and stipitate (crateriform); or dilated, flat, and without prominent margin (peltaform, of which the reniform is a variation); or convex with repressed margin (cephaloid); or between scutelliform and peltæform (disciform); or between scutelliform and cephaloid (tuberculate). When the thalline exciple is prolonged below into a footstalk, it is said to be pedicellate; a proper exciple in like manner prolonged is said to be stipitate. When the proper exciple is originally and typically closed, the apothecium receives the name of perithecium. In the Angiocarpi several thalamia are sometimes contained in the same exciple (composite apothecia); and in the Gymnocarpi, in like manner, several disks are sometimes confluent (symphycarpeous apothecia). The colors of the thallus in Lichenes are disposed by Fries in four series: 1. from pale green becoming glaucous; 2. from yellowish green becoming ochroleucous ; 3. from dark green becoming fuscous or olivaceous; 4. from pale yellow-green becoming lemon-colored. Each series has its peculiar variations. The glaucous runs into pale green, cerulescent, and white; the fuscous into dark green, olivaceous, cinereous, grayishfuscous, and dark chestnut; the ochroleucous into yellowish green. and albescent; the lemon-colored into pale yellow, orange-red, and vermilion-red.

SYNOPSIS OF THE GENERA.

Div. I. GYMNOCARPI, Schrader, Fries.

Apothecia open, disciferous. Thalamium originally disciform, or becoming so, contained in a thalline exciple or a proper exciple; disk normally persistent, ascigerous; sometimes originally pulveraceouscollapsed.

Tribe I. PARMELIACEÆ, Fr.-Apothecia rounded, from concave becoming explanate, scutelliform, rarely peltate. Disk somewhat waxy, persistent, contained in a thalline exciple. Subtribe 1. USNEEE, Eschw. - Disk open. Thallus subvertical, or pendulous-sarmentose, centripetal, without apparent hypothallus. 1. USNEA. Apothecia peltate; thallus with a solid medullary layer. 2. EVERNIA. Apothecia scutelliform; thallus fistulous, or with a cottony medullary layer.

3. RAMALINA. Apothecia orbiculate-subpeltate; disk pale, of nearly the same color with the thallus.

4. CETRARIA. Apothecia scutellate-peltate, oblique.

Subtribe 2. PARMELIEE, Eschw. -Disk at first closed, becoming at length discoid-open. Thallus horizontal, centrifugal, with a hypothallus.

5. NEPHROMA. Apothecia reniform, adnate to the under side of the lobes.

6. PELTIGERA. Apothecia peltæform, adnate to the upper side of the elongated lobes.

7. SOLORINA. Apothecia maculæ form, adnate to the disk of the

thallus.

8. STICTA. Apothecia scutelliform; thallus with cyphellæ, or discol ored spots, on the under side.

9. PARMELIA. Apothecia scutelliform; thallus without veins or cyphellæ beneath.

10. THELOTREMA. Apothecia urceolate-scutelliform, a discrete interior exciple veiling a rigescent disk.

11. GYALECTA. Apothecia urceolate, an elevated and discrete colored margin bordering a nigrescent disk.

Tribe II. LECIDEACEÆ, Fr. Apothecia rounded, a persistent

disk contained in an open proper exciple, which it finally covers, and becomes convex, cephaloid, and immarginate.

12. STEREOCAULON. Apothecia turbinate, at length cephaloid; podetia mostly solid.

13. CLADONIA. Apothecia at length cephaloid, inflated; podetia fistulous.

14. BEOMYCES. Apothecia capitate, globose, immarginate, velate. 15. BIATORA. Apothecia disciform, solid, with a waxy (originally

paler) exciple.

16. LECIDEA. Apothecia disciform, solid, with a carbonaceous, black proper exciple.

Tribe III. GRAPHIDACEÆ, Fr.-Apothecia of various form, an altered thalline carbonaceous proper exciple, or an originally proper exciple margining a gyrose and proliferous-papillate, or canaliculate disk.

17. UMBILICARIA. Apothecia orbiculate or lirellæform; thallus folia

ceous.

18. OPEGRAPHA. Apothecia lirellæ form; thallus crustaceous.

19. LECANACTIS. Apothecia irregular, at first open, with a pruinose thalline veil.

Tribe IV. CALICIACEÆ, Fr. - Apothecia orbiculate or globose, always open, margined by a proper exciple, the disk collaps. ing into naked sporidia; or without an exciple, the sporidia capituliform-compact.

20. TRACHYLIA. The carbonaceous exciple innate, with an ascigerous disk.

21. CALICIUM. The carbonaceous exciple free; disk compacted of naked sporidia.

22. CONIOCYBE. Exciple wanting; sporidia capituliform-compact.

Div. II. ANGIOCARPI, Schrader, Fries.

Apothecia closed, nucleiferous, pertuse and with an ostiole, or irregularly dehiscent; the nucleus included, subglobose, ascigerous. Tribe I. SPHÆROPHORACEÆ, Fr.- Apothecia formed of the intumescent apices of the thallus, closed, at length irregularly lacerate-dehiscent. Nucleus subglobose. Thallus vertical, fru

ticulose.

« AnteriorContinuar »