II. The Ovule of Stangeria paradoxa. 297 
tions have led to the conclusion that the recognition of these 
as definite bands in Stangeria was due to the sporangial wall 
not being quite mature, and that, although the epidermis in 
this position and extending down from the apex of the spo¬ 
rangium towards the lower surface has somewhat thicker 
walls than that on the sides of the sporangium, the differences 
do not warrant the close comparison made with any particular 
sporangium among Ferns, such as that of Angiopteris . 
With regard to the group of small isodiametrical cells 
situated at the apex of the sporangium, these further observa¬ 
tions have shown a considerable range of variation in Stangeria. 
As a rule the group consists of only a few cells with fairly 
thick colourless walls, surrounded by the brown thick-walled 
cells, which present no distinctive characters when they border 
on the apical group. It is this apical group which has usually 
been compared to the annulus of Osmunda and Angiopteris. 
But some of the microsporangia of Stangeria were found to 
present an apical group of larger size composed of fairly 
thin-walled cells. Around such a group as this the thicker 
walled brown cells form a definite and regular margin. 
Further, the series of cells immediately adjoining the apical 
group in these cases is characterized by its definiteness, and 
suggests a comparison with the annulus of the Schizaeaceae , 
in its less defined form, as seen in Mohria. It is not intended 
to imply by this comparison any actual relationship with the 
Schizaeaceae , but to suggest that, until more evidence is 
forthcoming as to the type of sporangium from which the Cycad 
microsporangia are derived, the nature of the apical group 
must be regarded as an open question. On the one hand, 
as is usually assumed, it might correspond to the annulus, 
on the other it may be more nearly comparable to the region 
of the sporangial wall above the annulus in the Schizaeaceous 
sporangium. It may be hoped that a comparative study of 
the other genera of Cycadaceae will throw further light on 
its true nature. 
