644 Kershaw . — Structure and Development of the 
development has been found in all the genera thus far investigated. The 
facts of ontogeny, therefore, do not support the supposed phylogenetic 
development of the integument. 
The vascular supply of the Cycad ovule was also held to agree closely 
with that of Lagenostoma . In certain genera of Cycads, Stopes 1 found 
that the bundles of the inner vascular series ran into the free part of the 
integument, and therefore this supply was held to be the equivalent of the 
integumental bundles of Lagenostoma , while the outer Cycad bundles were 
the equivalent of the cupule bundles. The vascular supply of Bowenia 
shows evidence of a conflicting nature which makes it impossible to accept 
the above comparison. In certain cases described the bundles of the inner 
vascular series ran into the nucellus, certainly only for a short distance; yet, 
if one accepts such a fact as a criterion, the inner vascular supply of Bowenia 
must be regarded as nucellar. Until more direct evidence on this point 
appears one can only leave the question of the exact position of the inner 
vascular series an open one. The general distribution and arrangement 
of the bundles of the Cycad seed, however, differ considerably from those 
in Lagenostoma. The bundles of the inner series in Cycads are almost 
concentric in structure, with little phloem, and form together a much branch- 
ing system around the nucellus ; the integument bundles of Lagenostoma , 
which were held to be their equivalent, were collateral with mesarch xylem, 
and ran without branching almost to the tip of the integument. These 
facts seem to show that the connexion between the Cycad ovule and 
Lagenostoma is not so close as has sometimes been assumed. 
On the contrary, the evidence strengthens the suggested 2 close re- 
semblance of the Cycad ovule to seeds of the Trigonocarpns affinity. It 
was seen above that as regards development and structure of the pollen- 
chamber Cycads agree closely with Trigonocarptis. The close correspon- 
dence between the integument of the two was emphasized by Scott and 
Maslen , 3 for in both it consists of three similarly differentiated layers. The 
outer fleshy layer of Trigonocarpns was lacunar, a condition which may well 
have led to the formation of mucilage passages, and also in this layer cells 
similar to the tannin cells of Cycads occur. The sclerotesta was differentiated 
into two regions of cells such as are found in many Cycads. Considering 
the vascular system — both have an outer supply of a constant number of un- 
branching collateral bundles and an inner, much branching system, which in 
Trigonocarpns directly enclosed the nucellus, and in Cycads lies usually 
in the plane of fusion of nucellus and integument. In both cases these 
bundles are small and consist only of a group of tracheides with little or no 
phloem. 
1 Stopes, loc. cit., 1904. 2 Scott, loc. cit., p. 649. 
3 Scott and Maslen : Structure of the Palaeozoic Seeds Trigonocarpns Parkins onii, See. Annals 
of Botany, vol. xxi, 1907, 
