Oil Some Stages i7i the Life History of Gnetum. 
265 
the number of free sac-nuclei available for the endosperm-fusion. There is 
some evidence for the existence of the first tendency within the Angiosperm 
group as at present constituted, and the fact that different degrees of polarity 
and of functional differentiation of the sac-nuclei are found among the 
Angiosperms may perhaps be regarded as evidence for the second. 
It is further suggested that the conditions preserved in the Grnetum-sac 
were similarly derived from those of an intrasporic prothallus whose funda- 
mental characters are found in the Cycads, Ginkgo, the Conifers, and 
Ephedra, by the operation of a similar tendency to shorten that portion of 
the life-cycle which lies between the macrospore-mother-cell and the func- 
tional gamete. 
It is, however, not suggested that the G-netum-sac is directly derived 
from that of the Conifers, nor the Angiosperm-sac from that of Grnetum. 
Eeviewing that portion of this hypothesis which touches the relations of 
the G-netales and the Angiosperms, Coulter remarks, " while the argument 
. . . is not convincing, it shows that the case is still open."* This is a 
fair summing up of the situation. The endosperm of the Angiosperm 
presents one of the outstanding problems of morphology. We suggest that 
its solution is to be sought along the lines now indicaated. But neither this 
nor any other hypothesis yet formulated can be accepted until it can muster 
in its support more convincing evidence than is yet forthcoming. 
Botanical Laboratory, 
South African College ; 
August, 1916. 
Bibliography. 
Berridge, E. M, 1909.—" Fertilisation in Ephedra altissima," Annals of Botany, xxiii, 
509. 
1911. — " On some Points of Resemblance between Gnetalean and Bennettitean 
Seeds," The New Phytologist, x, 140. 
■ and Sanday, E., 1907.—" Oogenesis and Embryogeny in Ephedra distachya." 
The New Phytologist, vi, 127. 
Bertrand, C. E., 1878. — " Etude sur les Teguments seminaux des vegetaux Phanero- 
games gymnospermes," Ann. d. Sci. Nat. (6), vii, 61. 
Blackman, V. H., 1898. -"On the Cytological Features of Fertilisation and Related 
Phenomena in Pinus sylvesiris, L.," Phil. Trans., B. cxc, 395. 
Bower, F. O. 1882. — "The Germination and Embryology of Gnetum Gnemon," Q.JM.S., 
xxii, 278. 
Brown, W. H., 1908.—" The Nature of the Embryo-sac of Peperomia," Bot. Gaz., xlvi, 
445. 
Caldwell, O. W., 1907— " Microcycas calocoma," Bot. Gaz., xlix, 118. 
Campbell, D. H., 1901.— "The Embryo-sac of Peperomia," Annals of Botany, xv, 103. 
1911. — "The Embryo-sac of Pandanus," loc. cit., xxv, 773. 
Caporn, a. St. C, 1916.—" A Note on the Male Inflorescence of a Species of Gnetum 
from Singapore," Ann. Bol. Herb., II, i, 15. 
* Coulter, 1916, p. 85. 
