142 BRITISH EOCENE ELORA. 



In Gnetum the species are trees or creeping shrubs, with jointed and knotty branches 

 and opposite entire leaves, which are not distinguishable from those of Dicotyledons. 

 The flowers are monoecious, produced on cylindrical, stalked, and jointed catkins, and spring 

 from the axils of the leaves. These catkins bear verticillate leaves, in the axils of which 

 the flowers, both male and female, are agglomerated. The former are composed of a 

 pair of bracts partially soldered together, forming an involucre from the middle of which 

 rises a staminal column, composed of two staminal leaves supporting pollen chambers 

 which correspond to the stamens of Dicotyledons, and are also in part the homologues of 

 microspores. The female flower is fashioned of altered bracts which combine in pairs to 

 form a double or even triple integument or perianth, the inner one being elongated like 

 a style. The ovule is in structure that of a Gymnosperm, but enveloped like an Angio- 

 sperm, though the ovary is formed of undeveloped bracts, instead of carpellary leaves. 

 It is solitary and the seed has an outer succulent coat. 



Welwitschia is a most singular and abnormal plant, inhabiting the arid regions of 

 South-west Africa, between the 14th and 23rd degrees of south latitude. Only a single 

 pair of leaves, after the cotyledonary leaves, is developed, which eventually become 

 leathery and split into shreds, attaining a length of six feet, and resting on the ground. 

 The intervening woody stock thickens and hardens, assuming an obconical form, taper- 

 ing rapidly towards the root, but never rising more than a foot above the ground, 

 though the table-like top may spread horizontally several feet in diameter. 



The circumference of the stem bears short-jointed branching flower-stalks, six to 

 twelve inches in height, each fork terminating in a small oblong monoecious cone, scarlet 

 when mature, under the decussate scales of which are flowers or seed. The female 

 flowers have naked ovules not essentially differing from those of other Gymnosperms. 

 The male flower is pseudo-hermaphrodite, containing anthers and an ovule, though the 

 latter is always abortive or unfertilised. Wehoitschia, through its male flowers, thus 

 presents the nearest approach to Angiosperms met with in any Gymnosperm. 1 Only one 

 species is known. 



No trace of anything referable to Gnetum has been found in our Eocenes, unless the 

 knotted and twisted stems found abundantly at Sheppey belong to it. A fruit from 

 Sheppey, apparently a thin oval shell of the size of a small nutmeg kernel, was labelled 

 " Gnetum " by Bowerbank ; but it was in fragments when I saw it and cannot be restored. 

 There are at present about fifteen species, confined to the tropics of Asia and America, 

 with two outliers in Africa and Eiji. 



The peculiarly-jointed and striated stems of Ephedra can, however, be picked out in 

 abundance from the masses of pyritised twigs left by the tide at Sheppey, and there is 

 no doubt that a species similar to that now living on the shores of the Mediterranean 

 forms part of the Sheppey fossil Flora. I have also come across a stone perforated with 



1 See Sir J. D. Hooker in ' Trans. Linn. Soc.,' vol. xxiv ; and Sach's ' Text-Book of Botany,' 

 " Gnetaceee." 



