THE GYMNOSPERMAE : CYCADALES, ETC. 749 



There are three Uving genera, sometimes classified as three distinct 

 famiHes, and with comparatively little in common except in the reproductive 

 structures. 



The genus Ephedra consists of shrubby, Broom-like plants with minute 

 leaves. There are about thirty-five species, divided between the Old and 

 the New Worlds. The species have mostly a restricted range and there 

 is none common to both sides of the Atlantic. In Europe they range round 

 the Mediterranean region and eastwards through Central Asia. In America 

 they are confined to the south-western United States and Mexico, also along 

 the Andes and across Argentina. 



The genus Gnetiirn includes trees, shrubs or woody climbers, the latter 

 form predominating. There are about thirty-four species scattered in a 

 belt of the Tropics from the East Indies, through West Africa to the Amazon 

 region, and they are invariably jungle plants. Their vegetative appearance 

 is entirely Angiospermic, and their large net-veined leaves cannot be dis- 

 tinguished from those of Dicotyledons. 



The genus Wehvitschia comprises the most remarkable living plants. 

 There is only one species, W. mirabilis, which is practically confined to the 

 Namib desert region of South-West Africa. It also occurs farther north, 

 growing in moist conditions and even under the shade of trees. The stem 

 resembles an enormous woody carrot the top of which is concave and may 

 reach 4 ft. in diameter. It is almost entirely buried in the sand and bears 

 only two long strap-shaped leaves which persist throughout life. 



It is obviously impossible to give a generalized account of so diverse a 

 group, but one common feature, however, deserves comment. AH three 

 genera have compound male strobili, i.e., the males, like the females, are 

 inflorescences, not single flowers, and this distinguishes them from almost 

 all other Gymnosperms. 



In the face of such striking divergences between members of one systematic 

 group it becomes necessary to consider in detail each genus separately. 

 The same objection applies with even greater force in dealing with 

 the Angiosperms, and from that point onwards our descriptions must be 

 general and comparative rather than particular. 



Ephedra 



All the species of Ephedra are woody, some are climbers and a few are 

 prostrate. Manv spread by rhizomes from underground buds. The branches 

 are green and slender and the leaves usually minute (Fig. 751). The whole 

 aspect of the plant is xeromorphic and strongly recalls a Cytisus. The leaves 

 are usually in opposite pairs, decussately arranged, and are joined (connate) 

 to each other at their bases to form a small sheath. Leaves in threes and 

 fours also occur, the latter rarely. 



The branches come from axillary- buds and are therefore in pairs or threes 

 according to the species. The first branches often come from the axils of the 

 cotyledons. Branching of the side shoots is confined to the lowest two or 



