484 MISS T. L. PRANKERD ON THE STRUCTURE OF 
more direct support is given by the fact that the preparations, the planes of 
which pass through the neck of the lagenostome, usually show a close 
approximation of the wall of the organ with the apex of the cone. In 
В. 26 (РІ. 23. fig. 12) this is so complete as to suggest that separation has 
never taken place. Here we are tantalized by the want of the next section, 
which would have passed across the base of the pollen-chamber and revealed 
whether ог no it contained pollen. If such were the fact, it would show 
how completely the “ stopper ” had closed the aperture in this ease. В. 21% 
(РІ. 28. fig. 14) is a similar, but more oblique, section across the neck of the 
lagenostome, which again shows the organ closed above; but here also we 
are faced with precisely the same difficulty—the section is a solitary one. 
Another preparation, К. 31, which also shows the closing of the lagenostome, 
is unfortunately but a fragment, and again we cannot be certain that it was 
pollinated. In the beautiful Battersea specimen (P1. 93. Но. 9)*, however, 
we have in a slightly oblique longitudinal section an almost completely 
closed lagenostome with a pollen-grain at the base on each side, proving 
that there must have been separation of the wall above, probably around the 
whole circumference f. 
No other suggestion has, I believe, been put forward as to the significance 
of this distinct modification of the central cone, and we may therefore 
view appropriate sections with the above idea in mind till a better be 
forthcoming. 
The vertical column of elongated cells extending from the * stopper" to 
the prothallus seems to correspond morphologically with the similar column 
described by Lang (8, р. 286) for the ovule of Stanyeria paradoxa, and by 
Kershaw (7) for that of Bowenia spectabilis, but its function in Lagenostoma 
is somewhat obscure. 
We now pass to the mode of formation of the pollen-chamber. Previous 
authors have spoken of the ‘ separation” of the wall from the central cone, 
but they give no suggestion as to how this took place. Та recent Cycads the 
pollen-chamber is formed by the disintegration of tissue in the apex of the 
nucellus ; but in Lagenostoma the pollen-chamber is of a very different type, 
and we must attach some significance to the highly specialized wall. 
Moreover, careful examination of the outer edges of the central cone and 
the wall strongly suggests rupture as the cause of the separation, and nothing 
like mucilaginous degeneration. Some preparations (R. 30a, R. 39, and 
* The photograph was made from a slide in the Battersea Polytechnic Collection, for the 
loan of which I am indebted to Miss L. J. Clarke. 
T The apex of the central cone is modified in a similar way in Z. Lomavii, The 
specimen R. 2 shows the “stopper” almost filling the neck of the lagenostome, as it could 
scarcely have done prior to pollination, which has obviously taken place. The section is 
figured in the paper (11) pl. 5. fig. 8 and pl. 9. fig. 21. 
