498 Arber and Parkin. — Studies on the 
of the Angiosperms. Here the megasporophylls carry on the work of 
pollen-collection. 
On our view the male fructification of Welwitschia is a complete pro- 
anthostrobilus. It possesses organs which, in common with other botanists, 
we regard as constituting a perianth. Above these, microsporophylls occur, 
and although no megasporophylls are to be found at the apex of the 
strobilus, a megasporangium is present. The strobilus is obviously a 
pro-anthostrobilus, for the office of pollen-collection would be entirely 
performed by the ovule, were it functional. 
The male strobilus of Welwitschia is in our opinion the most primitive 
of the Gnetalean fructifications. The female, and both the male and female 
strobili of Ephedra and Gnetum , have been derived from it by reduction ; 
one set of organs, either male or female, being entirely suppressed. These 
fructifications are therefore very reduced pro-anthostrobili, which have 
originated from amphisporangiate forms. Thus the application of the 
Strobilus Theory to the Gnetales offers a simple explanation of the pecu- 
liarities of their fructifications, which have hitherto proved so puzzling. 
We now proceed to inquire in some detail how far the evidence will 
support this view. 
The Perianth. 
In the fructifications of all three genera the sexual organs are sub- 
tended by and enclosed in envelopes (Text-fig. 2), the morphological inter- 
pretation of which has given rise to much divergence of opinion. 
The view that these structures in the male fructifications, and the 
outer series in the female, are of the nature of a perianth is a very old 
one. Linnaeus 1 referred to the envelope of Ephedra as a fleshy calyx. 
De Jussieu separated Ephedra , with Casuarina and Taxus , from the rest 
of the Coniferae on the presence of a f staminiferous 5 calyx . 2 
In regard to the male fructifications, these envelopes might either be 
looked upon as of the nature of a perianth, or merely as bracts with no 
phylogenetic significance. In the case of the female, all of them might be 
held to be equivalent to integuments, or the outer series, the homologues 
of either bracts, perianth, or even megasporophylls. It is from these pos- 
sibilities that we have to choose, and it may be worth while briefly 
reviewing previous opinions in this connexion. 
Robert Brown , 3 a great authority, decided as follows : c In Ephedra, 
indeed, where the nucleus is provided with two envelopes, the outer may, 
perhaps, be supposed rather analogous to the calyx or involucrum of the 
2 De Jussieu (i789), p. 41 1 . 
a Brown (’27), p. 455- 
1 Linnaeus (1751), p. 75 . 
