Trigonocarpus Skorensis, sp . nov. 
67 
5. Comparison with Cycads. 
Recent work on the Cycadean ovule , 1 and the additional facts regarding 
the structure of T rigonocarpus here brought forward, serve to emphasize 
the unmistakable relationship between the two groups. In the organization 
of the integument, differentiated into three layers, the agreement is extremely 
close, even as regards the broad structure of the stony layer which in Cycads 
as well as in Trigonocarpus is formed of longitudinally directed fibres on 
the inside, which at the outside become interwoven with horizontally directed 
elements . 2 Also, in the vascular, organization and the structure of the pollen 
chamber 3 the resemblances are particularly evident. 
The chief interest of the present work in this connexion results from 
the recognition of the short Cycadean type of sclerotic beak within the 
genus Trigonocarpus , and the presence of secretory elements situated in the 
sarcotesta of the latter, and resembling very closely the mucilage sacs of 
the modern group. 
The tendency for the non-vascular ribs to die out, of which an early 
stage is shown by T. Shorensis i reaches its culmination in the Cycadean 
family, where, too, the development of ribs in relation to the sarcotestal 
bundles, as found in T. Parkinsoni , likewise constitutes a prominent feature 
of certain genera. 
The absence of a nucellar system in the Lagenostomales is probably 
correlated with the fusion between testa and nucellus. How, then, are we 
to account for the retention of this same system under similar conditions in 
the Cycadean ovule ? The explanation seems to be found in the isolation 
of the nucellar and integumental systems from one another by the inter- 
vening sclerotesta, which thus prevents the latter from performing the 
functions of both. 
The suggestion advanced by Worsdell 4 that the fused integument and 
nucellus was brought about by a congenital fusion rather than that it arose 
as an intercalated zone of growth, as suggested by F. W. Oliver , 5 seems the 
more probable, both on the grounds there adduced and in view of the 
absence of any evidence in Cycads, comparable to that found in the 
Lagenostomales, of such having taken place. 
1 Kershaw : Structure and Development of the Ovule of Bowenia spectabilis. Ann. Bot., 
vol. xxvi, No. 103, 1912. 
2 Stopes : On the Double Nature of the Cycadean Integument. Ann. Bot., vol. xix, 1905, 
p. 564; Chamberlain: The Ovule and Female Gametophyte of Dioon. Bot. Gaz., vol. xlii, 1906, 
P. 33 2 - 
3 Kershaw, loc. cit., p. 643. 
4 Fasciation, its Meaning and Origin. New Phyt., vol. iv, 1905, p„ 38. 
5 The Ovules of the Older Gymnosperms. Ann. Bot., vol. xvii, 1903. 
F 3 
