317 



Geography. It is the opinion of M. Ad. Brongniart, that in the 

 earlier ages' of the world these plants attained a gigantic size, equalled only by 

 the timber-trees of our forests ; and it is certain that remains of what appear 

 to have been species of this tribe are abundant in the coal measuresj along 

 with Ferns. At the present day they do not exceed the height of 2 or 3 

 feet in any instance, and are usually weak, prostrate plants, having the 

 habit of Mosses. In geographical distribution they follow the same laws as 

 Ferns, being most abundant in hot humid situations in the tropics, and 

 especially in small islands. As they approach the north th§y become scarcer; 

 but even in the climate of northern Europe, in Lapland itself, whole tracts 

 are covered with Lycopodiiim alpinum and Selaginoides. 



Properties. Lycopodium clavatum and Selago excite vomiting ; the 

 powder contained in the thecse is highly inflammable, and is employed in 

 the manufacture of fireworks. According to M. Vastring, they are likely to 

 become of importance in dyeing. He asserts, that woollen cloths boiled. with 

 Lycopodiums, especially with L. clavatum, acquire the property of becoming 

 blue when passed through a bath of Brazil wood. Lycopodium Phlegmaria 

 is reputed an aphrodisiac. 



Examples. Isoetes, Lycopodium, Psilotum, Tmesipteris. 



CCLXVI. MARSILEACEiE. The Pepperwort Tribe. 



RhizocarpjE, Batsch. Tab. Aff. (1802); Agardh. Aph. 111. (1822) RhizospermyE, 



Roth. Dec. Fl. Fr. 3. 577- (1815) — Hydhopterides, Willd. Sp. PI. 5. 534. 

 (1810).-— Maksileace^., R. Brown Prodv. 166. (1810); Grev. Fl. Edinens. tlu. 

 .(1824) ; Ad. Brongn. in Diet. Class. 10. 196. (1826) ; Dec. and Duby, 542. (1828). 

 — SALyiNiE.^, Juss. in Mirb. Eltmens, 853. (1815.) 



Diagnosis. Flowerless plants, with their sporules enclosed in thecse, 

 contained within close involucra. 

 Anomalies. 



Essential Character — Creeping or floating plants. Leaves either petiolate and 

 divided (or petioles destitute of lamina), rolled up in vernation, or imbricated and sessile. 

 Reproductive organs enclosed in leathery or membranous involucra, and of two kinds, the 

 one consisting of membranous sacs, containing a body or bodies, which germinate, the 

 other of similar sacs, containing loose granules. 



Affinities. It is probable that this tribe, as now constituted, compre- 

 hends two exceedingly different forms of organisation, of which one is repre- 

 sented by Marsilea and Pilularia, and the other by Azolla and Salvinia. I 

 follow M. Adolphe Brongniart in this division, adopting from him many of 

 the succeeding observations. 



The tribe to which Pilularia and Marsilea belong consists of creeping 

 plants, having the circinate vernation of Ferns, with their reproductive organs 

 in indehiscent leathery cases, called involucra, springing either from the root, 

 or from the petioles of the leaves. These involucra are separated internally 

 by membranous partitions, and contain oval bodies of two kinds, one of which 

 has been called anthers, and the other capsules. 



Beautiful figures of Marsilea vestita and polycarpa have been published 

 by Messrs. Hooker and Greville, at t. 159 and 160 of their noble hones 

 Filicum. From these it is clear that the involucrum of the genus consists 

 of an involute frond, of the same degree of analogy to the true frond as a 

 carpellary leaf to a true leaf. It further appears that the reproductive bodies 

 arise from the veins of this involute frond, and are therefore analogous, as to 



