€26 Anatomy and Morphology, etc., o/* Welwitschia mirabilis. 



reduced perinucellary ring is formed at the base of the aborted ovule ; in it 

 two large bundles are especially conspicuous, and probably represent the 

 reduced vascular supply of the single integument, which is here regarded as 

 representing the outer integument of the female flower. 



The changes involved in the development of the fertile ovule consist 

 chiefly in the growth of the region between the origins of the two integu- 

 ments, and in the still greater enlargement of the region above the origin 

 of the inner integument resulting in the formation of the remarkable 

 nucellar beak. The micropylar tube or tip of the inner integument becomes 

 strongly cuticularised. The embryo-sac extends from the level of the origin 

 of the outer integument for some distance above the origin of the inner 

 integument, and projects into the nucellar beak. Its position with regard 

 to the two coverings thus corresponds roughly with the position of the 

 embryo-sac in Lagenostoma in relation to the cupule and inner integument. 

 The cupule is compared with the free outer covering of Welwitschia, and it 

 is pointed out that the greater growth of the apical region of the Welwitschian 

 ovule is probably correlated with siphonogamic fertilisation. The large 

 nucellar beak provides also more space for the elongation of the embryo-sac 

 and embryo, and may be regarded as the precursor of the well developed 

 apical region of the nucellus in Angiosperms. 



The seeds of Cardiocarpus and the Cycads are also compared with 

 Lagenostoma and Welwitschia. In all these seeds the inner system of bundles 

 appears to belong to the inner integument. 



The ovule of Welwitschia also shows some points of resemblance to that of 

 Bennettitcs. It is thought probable that the ovulate strobilus of the 

 Bennettitals is comparable with a telescoped cone of Welwitschia, and that 

 Williamsonia angusti/olia represents an intermediate stage in the telescoping 

 process. 



It is concluded that Welwitschia is probably connected with the Cycadean 

 series, with the Bennettitals, and with the ancestry of the Angiosperms. 

 It seems remarkable that while both kinds of sporangia in the Cycads, the 

 microsporangia in the Bennettitals, and probably both the ovules and 

 stamens in the Angiosperms are foliar, the ovules of Welwitschia and 

 Bennettites are commonly considered caulino. Possibly these also are 

 primitively foliar, and long ago became separated from the leaf and inserted 

 on the cone axis ; it is shown that the course of the bundles to some extent 

 supports this suggestion. 



