632 Kershaw. — Structure and Development of the 
sisted of about a dozen sporophylls, each with a pair of ovules, one of which 
is represented in natural size in Fig. 9. Very frequently one of the pair of 
ovules was malformed and had a very twisted, shrunken appearance, but was 
otherwise quite healthy. The prothallus and archegonia of such an ovule 
were normal. Possibly the distortion was the beginning of a late abortion, 
caused by the great pressure exerted on the ovules during the growth of the 
cone. The normal ovules are about 2 cm. long and i-8 cm. across. They 
are distinctly oval in shape with a prominently pointed micropylar tube. 
The surface of the ovule is smooth and covered with brown flecks due to the 
tannin sacs beneath the epidermis. 
The general relation of parts of such an ovule is seen in diagram- 
matic view in Text-fig. 13. The three layers of the integument are dif- 
ferentiated, the stone layer being represented by the closely dotted layer. 
Text -fig. 6. Diagrammatic transverse sections of 
the ovule, showing the vascular supply. (i) The 
base of the ovule. (2) Just below the point at which 
nucellus and integument become free. 
Text-fig. 7. Longitudinal 
section of sporophyll, showing 
vascular supply to the attached 
ovule. — Explanation in Text- 
figs. 8-12. 
The outer and inner series of vascular bundles are well developed. The 
free part of nucellus and integument is only a small portion of the whole 
ovule. In the pollen-chamber there are developing pollen-grains whose 
rooting ends have penetrated the tissues of the nucellus. The prothallus 
is of large size, usually about i-8 cm. in length, and has a ring of 5-7 
archegonia at the apex. 
An examination of the integument shows it to be thin compared 
with that of other Cycadean ovules of a similar age. The outer flesh 
forms more than half of the whole thickness, 1*4 mm. Indeed at the end 
of the micropyle almost the whole of the tissue is outer flesh. This layer 
of the integument is bounded by a regular layer of small epidermal cells 
with strongly cuticularized outer walls. The rest of the tissue consists 
