1132 Thoday .— The Female Inflorescence and Ovules of 
of the outer integument are all points of contrast with Welwitschia and 
probably indicate the more primitive nature of the Gnetum ovule. 
10. The attempt to refer the seed of Welwitschia to the same ground 
plan as that of such Pteridosperms as Lagenostoma and such recent seeds as 
the Cycads is thus supported by the study of Gnetum. Between Gnetum 
and Bennettites there are still more obvious resemblances. None of these 
forms are of course regarded as directly derived from one another, but the 
seed characters render it probable that they derive their origin from common 
ancestors. 
My thanks are due to Mr. Mangham for the five photographs forming 
PI. LXXXVII illustrating this paper. 
Botany School, Cambridge, 
July 28, 1911. 
ADDITIONAL NOTE. 
Since the above was written two publications have appeared which bear 
on the subjects discussed, and which require some notice here. 
I. Wieland’s most recent paper on the American Fossil Cycads ? 
‘ Further Notes on Seed Structures/ 1 is chiefly concerned with the minute 
structure of their integuments. His account of Beimettites Morierei , espe¬ 
cially his description of the base of the seed, is full of resemblances to 
G. africanum. But he seems quite convinced that the middle or stony 
layer of the seed, at any rate in Cycadeoidea , is continuous with the micro- 
pylar tube (see especially Fig. 5, p. 144), which is therefore not the pro¬ 
longation of the inner flesh only, as it should be were it to be closely 
homologized with the inner integument in Gnetum . On the other hand? 
he gives a diagram (Fig. 3 C, p. 141) showing the micropylar tube clothed 
with the stony palisaded layer, but made up mainly of thin-walled tissue. 
The latter may be chiefly closing tissue, but must consist partly of prolonged 
inner flesh ; he does not discuss the question fully. There appears to me 
nothing incredible in the suggestion (p. 1128 of the present paper) that the 
micropylar tube, so delicate in most species, should in Cycadeoidea have 
become protected by a firm hard layer derived from the outgrowth of some 
of the tissues of the outer integument. 
Whether or no the attempts at homologies between Gnetalean and 
Bennettitalean seeds made in the present paper prove of any ultimate value, 
the remarkable resemblances in the detailed structure of the integuments 
and micropylar tubes are too great to be lost sight of. 
II. Schusters paper 2 on ‘Weltrichia und die Bennettitales ’ contains 
1 The American Journal of Science, xxxii, 1911. 
2 Kungl. Svenska Vetenskapsakademiens Handlingar, Band 46, No. 11. Stockholm and 
Upsala, 1911. 
