44 Oliver and Salisbury. — On the Structure and 
there are three principal ribs, three secondary, and six tertiary. The six 
bundles subtend the last. 
In P olylophospermmn siephanense , Br., there are six major ribs and six 
minor, each with a bundle. 
If the origin of the integument here was similarly multiple, we must 
assume that there was complete fusion of the individual members before 
the inception of sclerization. This latter extended along the inner surface 
of the fused organs. The ribs may have been purely mechanical and 
utilitarian in origin, and their relation to the bundles of a similar nature 
to that which is exemplified in the leaf of a Cordaitean such as C. angulo- 
striatus , where sclerization has proceeded at both surfaces and produced 
prominent ribs at each bundle, and between each pair of bundles a secondary 
rib and two symmetrically placed tertiary ribs on either side. In modern 
Cycads, such as Meter ozamia spiralis and Encephalartos Altensteinii , the 
bundles in the outer flesh overlie the ribs of the sclerotesta . 1 If the integu- 
ment here be double, as some hold , 2 it could only be homologized on this 
view by the assumption that sclerization took place, in time, subsequent to 
the fusion of the outer and inner integuments. 
A further point of general interest as regards the testa, and perhaps of 
some considerable significance, is the flattening observed in the seed of 
Cono stoma oblongum\ this platyspermy is even further developed in Gnetopsis 
elliptica, where it is associated with a reduction of the number of bundles to 
four (Text-fig. u). The appearance of the transverse section of the latter 
seed could be readily obtained from the former if we suppose the two major 
ribs to have lost their bundles and the corresponding angles to have been 
flattened to a gentle curve. These facts, taken together with the general 
tendency exhibited in the group towards the reduction in number of the 
vascular strands accompanied by a corresponding reduction in the number 
of ribs or angles, point to the possibility of this tendency having been carried 
still further, resulting in the production of a seed with only two vascular 
strands and a testa exhibiting a bilateral symmetry comparable to that of 
Car diocar pits. But whether such a seed definitely referable to this chain 
of affinity be found or not, the facts seem to indicate that, whilst the terms 
‘ radiospermic ’ and ‘ platyspermic* have a definite use as morphological 
distinctions, our attitude towards them as criteria of taxonomic importance 
may require readjustment. 
The presence in Conostoma and Gnetopsis of the highly specialized layer 
we have termed the c blow-off’ seems to call for some explanation. Probably 
to be regarded as homologous with the peg-producing layer of Lagenostoma 
and the epidermis with its mucilage-containing hairs in Physostoma, its 
1 M. C. Stopes: Beitrage zur Kenntnis der Fortpflanzungorgane aer Cycadeen. Flora, 190^, 
p. 474. 
2 Coulter and Chamberlain, p. 158, Morphology of Spermophytes, 1901 ; M. C. Stopes, loe. cit. 
