502 
Arber and Parkin. — Studies on the 
microsporophylls of other Gymnosperms, either recent or fossil. There has 
been considerable divergence of opinion as to what corresponds exactly to 
a microsporophyll in these plants, as distinct from the microsporangia, and 
also as to the number of sporophylls present in each genus. The mor- 
phology appears to us to be rendered difficult by the great reduction and 
cohesion which has taken place. In Ephedra and Gnetum reduction has 
been carried to such a degree that a monosporangiate fructification has 
resulted, which further obscures the homologies. 
The male flower of W elwitschia seems to present the least diffi- 
culty. The male organs here at least are lateral structures. Hooker 1 
considered that six, partly united stamens, in one whorl, are present, each 
possessing a trilocular anther. This hexandry, he says, is a departure from 
the binary arrangement found elsewhere in this plant. McNab 2 disagreed 
with Hooker, and showed that a dimerous symmetry prevails, for, in 
development, the six male organs arise from two primordia placed later- 
ally, alternating with the inner perianth whorl. Strasburger, 3 though 
originally holding a different view, adopted McNab’s interpretation in 1879. 
We are also in agreement with this conclusion. 
The first point to be considered is the homology of these organs 
in the three genera. Here again we find that W elwitschia affords the clue. 
In that genus there arises from each of the two primordia a structure 
resembling a microsporophyll, and bearing three, stalked synangia. We do 
not propose to express any opinion as to whether this organ is derived by 
the fusion of three separate microsporophylls, or whether it is more truly to 
be regarded as a single, branched sporophyll. For the sake of clearness in 
comparison, we propose to speak of it as a unit. 
The male organs of all three genera can, on our view, be interpreted as 
derived from two such units. In W elwitschia, we find two units, each 
bearing three, stalked synangia. In Ephedra and Gnetum the two units are 
united, though in some species of the former genus they remain free for some 
distance above. 
This theory is that which has been clearly worked out by Thibout, 4 
who has given an admirable explanation of the homologies of the male 
organs in all three genera, and has shown the close connexion existing 
between them. Starting from Ephedra distachya, Linn. (T ext- fig. 3, 1 ), where 
the two units have each four synangia, which either cohere entirely, or 
remain somewhat free at the apex, we pass next to Ephedra fragilis , Desf. 
(Text-fig. 3, II), where one synangium (the inner lateral marked d in 
Text-fig. 3, I) of each unit is suppressed. This is the condition found in 
W elwitschia, where, however, the synangia are trilocular and stalked 
(Text-fig. 3, V). It may be pointed out, however, that in E. fragilis, this 
1 Hooker (’OS';, pp- 22 and 41. 2 McNab ( 73 ), p. 508. 
3 Strasburger (’ 79 ), pp. 133-4, footnote. 4 Thibout (’ 96 ), part iii, Pis. XV and XVI. 
