LIl] WELWITSOHIA 465 



persist as the only leaves throughout the long life of the plant, 

 attaining a length of 5 m. The tough lamina is torn into strips 

 by the wind and 'the extraordinary appearance of the shapeless 

 mass of coiled and twisted leaf-ribands standing out in bold relief 

 from the sharp glistening dead landscape passes description^.' 

 The venation is parallel and there are numerous cross-connexions, 

 some ending blindly in the mesophylP. Welwitschia is dioecious 

 and the flowers are borne in inflorescences with a dichasial branch- 

 system produced from pits on the crown of the stem; the female 

 inflorescences, which are larger than the male, reach a length of 

 30 cm. and bear cones about 7 cm. long. The female flowers occur 

 singly in the axils of bracts which form four orthostichies giving 

 a four-angled form to the cones. Each flower may produce two 

 small leaf-rudiments*, but the flower proper consists of an ovule 

 with two envelopes; the outer, called by Hooker the perianth, is 

 considerably extended tangentially and ia the ripe seed forms a 

 wing-like appendage producing an appearance almost identical 

 with that of some Samaropsis seeds. The inner integument is 

 prolonged upwards hke a long and slender hollow bristle for a 

 distance of 4 — 5 mm. beyond the upper edge of the subtending 

 bract. The inner envelope has no vascular supply. The secretion 

 of sugar in the micropylar tube attracts the pollinating insect 

 Odontopus sexpunctulatus . The staminate cones are smaller and 

 the subtending bracts connate. The outer envelope of the flower 

 is formed of two membranous segments without vascular bundles 

 which may be styled lateral prophylls of the axillary shoot : internal 

 to these are two fused members forming a sac-like investment 

 with free rounded lobes also without a vascular supply. Within 

 these perianth-segments is the staminal tube bearing six free 

 stamens each supplied with a vascular bundle and bearing a 

 terminal trilocular synangium (fig. 818). The centre of the flower 

 is occupied by a pyriform ovule surrounded by a thin integument 

 continued as a slightly kinked stylar tube terminating in a flat 

 stigmatic disc 1 mm. in diameter. There is no embryo-sac but 

 the nucellus acts as a nectary, the drop-mechanism of the functional 



1 Pearson (Oe^) p. 270. 



2 de Bary (84) A. fig. 157; Sykes (lO^); Takeda (13^). 

 ^ Lignier and Tison (12). 



s. rv 30 



