232 



GNETACEiE. 



[Gymnogens. 



Order LXXVI. GN E TAG EiE.— Joint Firs. 



Gneteae, Bliime, in Ann. Sc. 2. Ser. 2. 105. (1834 .— Gnetacese, Lindl. in Bot. Reg. 1686. {Julp, 1834) ; 



Endl. Gen- Ixxix. ; Meisner, p. 352. 

 BixQmsis.—Gymnogens with repeatedly hranched jointed stems, simple net-veined leaves, 

 I. celled anthers opening by pores, and the membrane next the micleus protruded.^ 

 Small trees very much branched, or sarmentose shrubs, secreting watery, not resinous 



Fig. CLXIII. 



matter, with opposite or clustered branches, and 

 thickened separable articulations. Leaves oppo- 

 site, entire, with anastomosing, reticulated veins ; 

 sometimes very minute and scale-shaped. Wood 

 ^\^th the ligneous tissue marked with circular 

 disks. Flowers $ $, arranged in catkins or 

 heads, surrounded by opposite decussating 

 Fig. CLXII. scales which are connate at the base, or altogether 



consohdated into a horizontal ring. $ Calyx 

 1 -leaved, transversely slit at the end, projectmg from its bottom a monadelplious fila- 

 ment bearing 1 -celled anthers, bursting longitudinally and centrally, so as to form a 

 pore. Pollen (in Gnetum, simple, smooth, oblong, Griffith), in Ephedra ellipsoid, with 

 6 longitudinal furrows. $ altogether naked, or sheltered by a false calyx consisting 

 of two scales, more or less combined, each of which sm-rounds one or two flowers. 

 Ovary 0. Ovule pointed by a style-like process formed from a third membrane sur- 

 rounding the nucleus. Seed drupaceous, before matm'ity pierced at the point and ter- 

 minated by a style-shaped protruded process ; finally pointless. Seed-coat thickish, 

 either altogether leathery, or shelly, or fibi'ous internally, and succulent externally ; in 

 Gnetum lined by acicular woody tissue. Embryo dicotyledonous, in the middle of 

 fleshy albumen ; radicle superior. 



Conifers and Cycads present features so peculiar that their separation from all other 

 Orders is a point concerning which there can be no diff'erence of opinion. It is indeed 

 difficult to trace a plain transition from them to the other parts of the Vegetable 

 Kingdom in wliich perfect sexes are present. There exist, however, a few plants, not 

 very similar to each other in appearance, bearing the names Gnetum and Ephedra, in 

 which we find precisely the structure and habit that would be wished for by a theorist 

 searching for evidence to bring Gymnogens into communication with true Exogens ; 

 for one of them has all the appearance of a Chloranth, and the other of a Casuarina ; 

 and yet both retain the true peculiarities of G}Tnnogens. These are called Gnetacese, 

 and may in Enghsli be termed Joint Firs, for they are closely allied to Conifers, but are 

 distinctly known by their stems being jointed at every node. In these plants there is 

 little tendency to form cones, and in the genus Gnetum the development of the ovule is 

 so pecuhar that botanists at one time, myself included, supposed that the real ovule 

 was in tinith an ovary pierced at the summit, for it consists of an exterior shell of 

 considerable thickness and of a green colour ; within which is a thimier envelope through 

 which passes a tubular projection fringed at the point, and within these lies a nucleus, 

 as is represented in the accompanying figure of the yomig ovule of Gnetum Bininonia- 

 num, copied from an unpublished dra^\ing by INIr. Griffith. So that this sort of ovule 

 has 3 distinct integuments, clear of the nucleus. It is to Mr. Griffith that I owe the 

 knowledge of the true natm-e of these plants. In a most elaborate unpubUshed Memoir 



Fig. CLXII.— Gnetum Gnemon ; 1. a section of an ovule showing the three membranes, of which the 

 innermost protrudes in the form of a stigma . 

 Fig. CLXIII.— A thin section of the wood of Gnetum Gnemon, highly magnified, after A. Brongniart. 



