930 
Further Observations on Welwitschia.* 
By H. H. W. Pearson, 8ce.D., F.LS. 
(Communicated by Professor A. C. Seward, F.R.S. Received July 29,— 
Read November 12, 1908.) 
(Abstract. ) 
The material which forms the subject of this investigation was collected at 
Welwitsch and Haikamchab, in Damaraland, in January and February, 1907. 
Macrospores and embryo-sacs are frequently present in the pith region of 
the female cone-axis. This confirms the view, already adopted by most authors, 
that the ovule of Welwitschia is cauline. Sporogenous cells have not been 
found in a similar position in the male cone. 
It is suggested that the female cone and the male flower are seamen by 
reduction and specialisation from an amphisporangiate strobilus of a type 
similar to that of Bennettites. 
At the end of the free nuclear division the embryo-sac contains about 1024 
nuclei which are equivalent in all visible characters. Cleavage of the 
cytoplasm occurs, resulting in the septation of the whole sac into compart- 
ments. Those near the micropylar end contain few nuclei which are 
functionally sexual; most of those of the lower three-fourths enclose many 
potentially sexual nuclei. The former send out embryo-sac-tubes into the 
nucellar cone and into them pass the cytoplasm and free nuclei; all the 
nuclei in each of the latter fuse so that each compartment becomes a 
uninucleate cell. The compartments containing the fusion-nuclei form the 
primary endosperm, whose later growth is distributed over two periods, one 
before and the second after fertilisation. The endosperm of Gnetum is 
probably formed in the same way. In respect of the morphological character 
of the endosperm, Gnetum and Welwitschia are widely separated from 
Ephedra, in which the endosperm is a prothallus of the normal gymnosperm 
type. It is suggested that the endosperm of the primitive angiosperms was 
homologous with that of Welwitschia. 
The embryo-sac-tubes meet the pollen-tubes in the lower half of the 
nucellar cone. Fertilisation occurs within the generative cell. 
The generative cell enlarges after leaving the pollen-grain and its nucleus 
divides. The daughter nuclei are functional gametes. 
Several oospores are commonly formed in each nucellus. The cytoplasm of 
* Assisted by a grant from the British Association. 
