328 cxxviii. GNETACE^ (Pearson). [Ephedra. 



Order CXXVIII. GNETACE-ffi. 



(By H. H. W. Pearson.) 



Dioecious or monoecious. Florets (flowers) diclinous or pseudo- 

 bisexual, few or many in axillary, rarely terminal, unisexual or 

 bisexual spikes. Male floret (pseudo-bisexual in Welwitschia) : 

 Envelope formed of one pair or two decussating pairs of scales, free 

 or united. Stamens 1-8 with the anthers sessile or subsessile on the 

 summit of a stout central axis or (in Welwitschia) 6 with the filaments 

 connate at the base around a central superior barren ovule. Female 

 floret : Envelope an ovary-like utficle. Ovule naked, erect, ortho- 

 tropous with a single integument produced into an elongated tubular 

 micropyleandprotrudingthroughtheorificeof the utricle, withor with- 

 out an aril. Seed albuminous, enclosed at maturity in the hardened 

 utricle which is either differentiated into a fleshy outer and a hard 

 inner layer, or entirely coriaceous and sometimes {Welwitschia) pro- 

 duced lateralh^ into 2 wings. Embryo straight with 2, rarely 3, 

 cotyledons.- — Erect or scandent virgate or leafy shrubs, trees or woody 

 climbers or (in Welwitschia) a woody plant of unique form consisting 

 of a stout tuberous hypocotyl and an early arrested depressed stem 

 apex, with true vessels in the secondary wood, without resin canals. 

 Foliage leaves 2 or more, rarely in whorls of 3, opposite, simple. 

 Spikes at the time of pollination gi'cenish or yellowish, rarely vividly 

 coloured {Welwitschia). Seeds with their envelopes more or less 

 enclosed in dry or fleshy cones or exposed and drupe-like {Gnetum). 



Genera 3 ; species 50-60, mainly in the tropics and subtropics of both hemi- 

 spheres. 



The group as defined above covers an extremely wide range of generic 

 characters ; when these are more completely known it will perhaps be necessary 

 to subdivide it into at least two Natural Orders, 



Tribe I. EPREBROIBE^.— Leaves usually all, or all but those of the seedling, 

 reduced to scales. Stems longitudinally grooved or striated. Embryo not 

 developing a "feeder " during germinatiov . 



Only Tropical African genus 1. Ephedra. 



Teibe II. GNETOIDE^. — Leaves large Stems not longitudinally grooved. 

 Embryo developing a "feeder " during germination. 



Trees, shrubs or lianos with more than one pair of 



fohage leaves. Pollen spherical 2. Gnetum. 



Plant body mainly a much thickened woody hypo- 

 cotyl with a single pair of foliage leaves. Pollen 

 ellipsoid 3. Welwitschia. 



1. EPHEDRA, Linn. ; Benth. et Hook. f. Gen. PI. iii. 418. 



Usually dioecious. Florets unisexual. Male florets in 2-12 pairs, 

 crowded in short rounded (rarely angular) spikes, in the axils of 



