318 PROF. F. W. OLIVER ON THE STRUCTURE 
axiale tardive, où se trouve un noyau? mal defini, appartenant peut-être à un Anthéro- 
zoide. Dans la région polaire on remarque un bourrulet circulaire £.p. *, se prolongeant 
en un tube court et représentant les restes d'un tube pollinique ; autant qu'on en peut 
juger par transparence, ce tube serait en relation avec la cellule axiale.” And further, 
* Il ne serait pas invraisemblable que les gros grains de pollen des Stephanospermum et 
des Aitheotesta aient ainsi produit un tube pollinique permettant la sortie des Anthéro- 
zoides emprisonnés dans une enveloppe épaisse et résistante.” 
In regard to ZEfheotesta no comment is called for here, as this seed has not come 
"under my observation. As regards Stephanospermum akenioides I have described in 
detail the critical preparations. That the body in the central space is nuclear in nature 
seems open to question, as indeed does the cellular nature of the space itself. It would 
seem possible that M. Renault may have had under observation pollen-grains of Stephano- 
spermum akenioides sharing a condition of preservation corresponding to that represented 
in Pl. 44. figs. 32, 33, & 34. This, taken in connection with a tube-like orifice attached 
to one pole in the case of Ætheotesta, obviously suggested the inference which 
M. Renault draws, evidently with some reserve. 
It may be pointed out that papilla-like outgrowths are not infrequent on the pollen- 
grains of S. akenioides, but they are not localised to a pole or any other spot in particular. 
One such is readily seen with a hand-lens on the lower side of the large pollen-grain 
in fig. 15. Another is present on the same grain immediately behind the foreign 
pollen-grain, and, of course, not shown in the photograph. The length of these little 
tubes does not exceed 20-25 w. Whether they be mere accidents of preservation or the 
simple pollen-tubes of unspecialised multiple pollen-grains must remain, for the present, 
an open question. 
Some allusion has been made to the perforation of the dissepiments in the interior of 
the pollen-grain. That they were abundant is seen from fig. 33, w. The raggedness of 
the walls eut in seetion, both here and in figs. 32 and 34,is due to the same cause. That 
these perforations are in any way connected with the liberation of possible antherozoids, 
can only be a matter of conjecture. The contents of the cells are not preserved in any 
of the specimens of S. akenioides that have passed through my hands. On the other 
hand, the fenestration of the walls may be readily conceived as the result of post-mortem, 
bacterial, or other destructive agency. Perforations of that kind are common enough in 
cuticularised epidermal membranes, parenchyma, Ae, in the Grand’ Croix pebbles. It 
is quite possible that in this species the seeds are preserved at a stage anterior to that at 
which antherozoids were liberated. But in any case the perforation of these internal 
walls is not wholly intelligible on any hypothesis of dehiscence; for, in addition to 
actual tubes, large openings are found in the outer wall of the grain, quite adequate for 
the exit of antherozoids. These have been figured by Renault T for Dolerophyllum, 
and attributed by him to bacterial agency; those produced here are in essential 
agreement. The only inference that can be safely drawn respecting the holes in the 
internal walls is that the walls of the pollen-grain complex were readily destructible, 
* This refers to a figure showing a pollen-grain bearing a small excrescence at one pole. 
t ‘Flore fossile d'Autun et d'Épinac, p. 269. 
