750 CCXXIV. CYCADB^. 



column ; anthers witli 2-4 cells, opening at the top by as many pores or valvules ; 

 ovule solitary, sometimes in the centre of the stamens {Welwitschia) and then abor- 

 tive, sessile, erect, orthotropous ; fi-imine membranous, open or notched at the top 

 (exostome) ; secundine exserted as a styliform tube which expands into a perforated 

 stigma-like more or less persistent disk {endostome). Seed with coriaceous or fleshy 

 testa. Embryo antitropous, in the apex of a fleshy albumen ; radicle superior. 



GENEEA. 

 Gnetum. Ephedra. Welwitschia. 



Some Gnetacecs, by the pinnate and anastomosing nerves of their leaves (Gnetum), and by the 

 structure of their wood-fibres, which, like those of Conifercp, are marked with a series of disks, but 

 are associated with large punctate vessels, establish the passage from Coniferce to the other Dicotyledons, 

 and in particular to Casuarinem through Ephedra, and to ChloranthecB through Gnetum. 



Gnetum Gnemon, faniculare, edule, and Brunonianum are aU natives of tropical Asia ; G. urens and 

 nodiflorum, &c., of Guiana. Ephedra inhabits temperate regions of both hemispheres, affecting salt deserts 

 and the edges of torrents; some species ascend into the alpine region, both in Europe (E. helvetica) and 

 America (E. andina) [and E. vulgaris in the Himalayas]. \E. distaehya, alata, altissima, fragilis, 

 campylopoda, and vulgaris inhabit the Mediterranean region. E. andina, americana, triandra, &c., are 

 American.] 



The most curious of the Gnetacece, and perhaps of all Dicotyledons, is that which was discovered a 

 few years ago on the west coast of Africa, near Cape Negro, by Dr. Welwitsch. It never exceeds a foot 

 in height, but the stem is often more than four feet in diameter. It bears no appendages but 

 its two cotyledons, which last throughout its life, i.e. more than a century, and in time grow to an 

 extraordinary size, attaining six feet in length and two to three in width ; they are green, very coriaceous, 

 and torn by the wind into numerous segments which spread out upon the earth. Along the margin of its 

 enormous platform-like stem, marked with concentric circles, rise short dichotomous floral pedimcles, the 

 branchlets of which bear terminal catkins or young cones, with brilliant scarlet bracts, imbricate in four 

 rows, each containing a flower. After flowering the cones enlarge, and attain about two inches in length 

 and one in diameter. This bizarre plant is named ioumho by the natives. We have taken all the dis- 

 sections from the valuable work of Dr. Hooker. 



The Ephedra are of little use to man ; the flowering branches of the Mediterranean species were 

 formerly used as styptics. Gnetum yield textile fibres more tenacious than those of hemp. The leaves 

 and fruit of G. Gnemon, which is cultivated in Amboyna and Java, are eaten as a vegetable. The 

 branches of G, urens contain a limpid somewhat mucilaginous potable juice; its seeds, when cooked and 

 baked, are edible. 



CCXXIV. CYCADEJE. 



(Ctcade^, Persoon, Br., L.-C. Richard.- — Ctoadaceje, Lindl. — Ctoadeace.«, Endlicher. 



— Ttmpanoohbt^, Martins.) 



Flowers dioecious, achlamydeous. Tlowees g , in terminal cones, and formed of 

 scales bearing on their dorsal face numerous 1-celled anthers. Flowers ? reduced to 

 naked orthotropous ovules, sometimes solitary, erect, inserted in the crenatures of velvety 

 foliiform appendages, sometimes geminate, inverted, on the inner face of peltate scales. 

 Seed albuminous. — Stem woody. Leaves pinnate, crowning the stem. 



Large or small trees, elegant, very long-lived. Stem usually simple, straight, 



