absolutely indispensable that it should be fully understood by those who wish to read the systematic writers upon the subject:

1. Apothecia, are shields of any kind.

2. Scutellum, is a shield with an elevated rim, formed by the thallus. Orbilla is the scutellum of Usnea.

3. Pelta, is a flat shield without any elevated rim, as in the genus Peltidea.

4. Tuberculum, or cephalodium, is a convex shield without an elevated rim.

5. Trica, or Gyroma, is a shield, the surface of which is covered with sinuous concentric furrows.

6. Lirella, is a linear shield, such as is found in Opegrapha, with a channel along its middle.

7. Patellula, an orbicular sessile shield, surrounded by a rim which is part of itself, and not a production of the thallus, as in Lecidea. D. C.

8. Globulus, a round deciduous shield, formed of the thallus, and leaving a hollow when it falls off, as in Isidium. D. C, 9. Pilidium, an orbicular hemispherical shield, the outside of which changes to powder, as in Calycium. D. C.

10. Podetia, the stalk-like elongations of the thallus, which support the fructification in Cenomyce.

11. Scypha (oplarium, Neck.), is a cup-like dilatation of the Podetium, bearing shields on its margin.

12. Soredia (globuli, glomeruli), are heaps of powdery bodies lying upon any part of the surface of the thallus ; the bodies of which the soredia are composed are called conidia by Link, and propagula by others.

13. Cystula, or Cistella, a round closed apothecium, filled with sporules, adhering to filaments which are arranged like rays around a common centre, as in Sphærophoron. 14. Pulvinuli, are spongy, excrescence-like bodies, sometimes rising from the thallus, and often resembling minute trees, as in Parmelia glomulifera. Greville.

15. Cyphella, are pale tubercle-like spots on the under surface of the thallus, as in Sticta. Grev.

16. Lacunæ, are small hollows or pits on the upper surface of the thallus.

Grev.

17. Nucleus proligerus, is a distinct cartilaginous body, coming out entire from the Apothecia, and containing the sporules. Grev.

18. Lamina proligera, is a distinct body containing the sporules, separating from the apothecia, often very convex and variable in form, and mostly dissolving into a gelatinous mass. Grev.

19. Fibrillæ, are the roots.

20. Excipulus, is that part of the thallus which forms a rim and base to the shields.

21. Nucleus, is the disk of the shield which contains the sporules and their cases.

22. Asci, are tubes, in which the sporules are contained while in the nucleus.

23. Thallodes, is an adjective used to express an origin from the thallus: thus, margo thallodes signifies a rim formed by the thallus, excipulus thallodes a cup formed by the thallus.

24. Lorulum, is used by Acharius to express a filamentous, branched thallus.

25. Crusta is a brittle crustaceous thallus.

26. Gongyli, are the granules contained in the shields, and have been thought to be the sporules by which lichens are propagated: but this is doubted by Agardh.

8. Alga and Characea.

These, with fungi, constitute the lowest order of vegetable developement: they vary in size from mere microscopic objects to a large size, and are composed of cellular tissue in various degrees of combination; some are even apparently animated, and thus form a link between the two great kingdoms of organised matter. Their sporules are either scattered through the general mass of each plant, or collected in certain places which are more swollen than the rest of the stem, and sometimes resemble the pericarpia of perfect plants. The terms used in speaking of the parts of Algae are the following:

1. Gongylus; a round hard body, which falls off the mother plant, and produces a new individual: this is found in Fuci. W.

2. Thallus; the plant itself.

3. Apothecia; the cases in which the organs of reproduction are contained.

4. Peridiola, Fr.; the membrane by which the sporules are immediately covered.

5. Granula; large sporules, contained in the centre of many Algæ; as in Gloionema of Greville. Crypt. fl. 6. 30. 6. Pseudoperithecium; terms used by Fries to express such 7. Pseudohymenium ; coverings of Sporidia as resemble in figure the parts named perithecium, hymenium, and peridium in other plants: see those terms.

8. Pseudoperidium;

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9. Sporidia; granules which resemble sporules, but which are of a doubtful nature. It is in this sense that Fries declares that he uses the word: vide Plant. homonom. p. 294.

10. Phycomater, Fries; the gelatine in which the sporules of Byssaceæ first vegetate.

11. Vesicula; inflations of the thallus, filled with air, by means of which the plants are enabled to float.

12. Hypha, Willd.; the filamentous, fleshy, watery thallus of Byssaceæ.

13. Nucula; one of the apothecia of Characeæ; described by

Greville to be a sessile, oval, solitary, spirally striated body, with a membranous covering, and the summit indistinctly cleft into five segments, containing sporules. 14. Globules; the second organ of Characea; the excellent observer last quoted describes it as a minute round body of a reddish colour, composed externally of a number of triangular (always?) scales, which separate, and produce its dehiscence. The interior is filled with a mass of elastic, transversely undulated filaments. The scales are composed of radiating hollow tubes, partly filled with minute coloured granules, which freely escape when the tubes are injured: their nature is wholly unknown, and, I believe, hitherto unnoticed.

15. Coniocysta; tubercle-like closed apothecia, containing a mass of sporules.

9. Fungi.

The structure of these plants is yet more simple than that of Algæ, consisting of little besides cellular tissue, among which sporules lie scattered. Some, of the lowest degree of developement, are composed only of a few cellules, of which one is larger than the rest, and contains the sporules; others are more highly compounded, consisting of myriads of cellules, with the sporules lying in cases, or asci. Notwithstanding the extreme simplicity of these plants, writers upon fungi have contrived to multiply the terms relating to them in a remarkable manner. The following are all with which I am acquainted :

1. The pileus, or cap, is the uppermost part of the plant of an Agaricus, and resembles an umbrella in form.

2. The stipes, is the stalk that supports the pileus. 3. The volva, or wrapper, is the involucrum-like base of the

stipes of Agaricus. It originally was a bag enveloping the whole plant, and was left at the foot of the stipes when the plant elongated and burst through it.

4. The velum, or veil, is a horizontal membrane, connecting the margin of the pileus with the stipes: when it is adnate with the surface of the pileus, it is a velum universale; when it extends only from the margin of the pileus to the stipes, it is a velum partiale.

5. The annulus, is that part of the veil which remains next the stipes, which it surrounds like a loose collar.

6. Cortina, is a name given to a portion of the velum which adheres to the margin of the pileus in fragments.

7. The hymenium, is the part in which the sporules immediately lie; in Agaricus, it consists of parallel plates, called lamellæ, or gills; these are adnate with the stipes, when the end next it cohere with it: when they are adnate, and at the same time do not terminate abruptly at the stipes, but are carried down it more or less, they are decurrent; if they do not adhere to the stipes, they are said to be free.

8. Stroma, is a fleshy body to which flocci are attached; as in Isaria and Cephalotrichum.

9. Flocci, are woolly filaments found mixed with sporules in the inside of many Gastromyci. The same name is also applied to the external filaments of Byssaceæ. 10. Orbiculus, is a round flat hymenium contained within the peridium of some fungi; as Nidularia.

W.

11. Nucleus, is the central part of a perithecium.

12. Sporangium, is the external case of Lycoperdon and its allies.

13. Sporangiola, are cases containing sporidia.

14. Perithecium, is a term used to express the part which contains the reproductive organs of Sphæria and its co-ordinates.

15. Peridium, is also a kind of covering of sporidia; peridiolum is its diminutive.

16. Ostiolum, is the orifice of the perithecium of Sphæria. 17. Sphærula, is a globose peridium, with a central opening, through which sporidia are emitted, mixed with a gelatinous pulp.

18. Capillitium, is a kind of purse or net, in which the sporules of some fungi are retained; as in Trichia. W.

19. Trichidium, or pecten, is a tender, simple, or sometimes branched hair, which supports the sporules of some fungi; as Geastrum. W.

20. Asci, are the tubes in which the sporidia are placed; ascelli or thecæ are the same thing.

21. Sporidia, are the immediate covering of sporules; sporidiola are sporules.

22. Thallus, or thalamus, is the bed of fibres from which many fungi arise.

23. Mycelia, are the rudiments of fungi, or the matter from which fungi are produced.

P