On Some Stages in the Life History of Gnetum. 
245 
good for this genus also. Karsten figures a generative cell of an unnamed 
species with a female nucleus lying in its protoplasm,* but free male nuclei 
are shown in the embryo-sacs of G. Bum]jhianum,f and Lotsy describes the 
passage of the generative nuclei into the sac, J and states that the fusion 
nuclei surround " themselves with a rather dense mass of protoplasm, which 
can be plainly distinguished from the protoplasm of the embryo- sac." § 
There appears to be a tendency to reduce the protoplasm of the male cell in 
the Grymnosperms.|| If, therefore, the male gamete is a free nucleus in 
Grnetum while in Welwitschia the whole cell is concerned in fertilisation, the 
difference is of interest. It has been suggested that an ancient character 
has reappeared in Welwitschia,^ probably as an adaptation to a unique 
method of fertilisation, itself perhaps part of a general adaptation to 
extremely xerophytic conditions.** It must nevertheless be regarded as not 
unlikely that, as is suggested by Karsten, the same character may be found 
in some species of G-netum. 
In G. Gnemon the oospore produces a single proembryo.ff In other 
cases {G. ovalifolium, G. Rumphianum) the oospore immediately undergoes 
a series of successive free nuclear divisions from which there results a mass 
of proembryos.:]:^ This appears to be the case in G. africanum, in which a 
mass of cells, believed to be proembryos, are frequently seen near the 
summit of the endosperm in ovules with a single pollen-tube. In view of 
the behaviour of the oospore in Ephedra and Welwitschia respectively, it 
will be of some interest should the occurrence of both these cases in G-netum 
be confirmed. 
The proembryo becomes a long tubular cell, whose direction of growth 
is very irregular, but in general by way of the axial cylinder of the endo- 
sperm towards the chalaza. The single nucleus gives rise to a small number 
of free nuclei (Plate L, figs. 27, 28), which is probably a general character 
in G-netum as it is in Ephedra and Welwitschia. Karsten figures a pro- 
embryonal tube of an unnamed species of Gnetum with two free nuclei § § and 
implies that a similar stage is found in G. Gnemon and G. funiculare. Lotsy 
shows free nuclear stages in G. Gnemon,\\\\ and in G. ula,^^ but with regard 
* Karsten, 1892, fig. 12. 
t Karsten, 1893, fig. 71. 
+ Lotsy, 1899, p. 95. 
§ Lotsy, loc. cit., p. 96. 
II Nawaschin and Finn, 1912. 
1[ Nawaschin and Finn, loc. cit., p. 50. 
** Pearson, 1909, p. 387. 
tt Lotsy, 1899, p. 97, fig. 55. 
t+ Karsten, 1892, p. 239 ; 1893, p. 372. 
§§ Karsten, 1892, p. 230, fig. 29. 
II II Lotsy, 1899, fig. 50. 
Lotsy, 1903, p. 399, figs. 8-12. 
