482 MISS T. L. PRANKERD ON THE STRUCTURE OF 
Lagenostoma, though the author gives some reasons for regarding the stone 
layers as belonging morphologically to the outer flesh. In their recent 
excellent text-book (6, p. 128), Coulter and Chamberlain again draw a 
distinction between the stone layers in the two types, for while in the Cycad 
it is a “complex tissue several cells thick," in Layenostoma it is “simply a 
modified epidermis.” But if the facts given above (pp. 466-470) are accepted, 
this seems scarcely allowable as a description of the hard tissue in our 
seed. The reasons for regarding the hypodermal layer as consisting of 
hard fibres have been fully given, and it seems doubtful whether the well- 
defined epidermis was really hard at all; on the whole it is more suggestive 
of being glandular or secretory in its nature. However this may be, it 
would certainly undergo some modification after fusion with the cupule, as 
any excretory function would inevitably be lost, and it may quite well have 
become sclerified even if not originally so. This would perhaps explain 
why “differentiation and selerification of the stone-cells start in the layers 
on the inner side and extend to an outward direction” (18, p. 564). At 
any rate there seems no decisive evidence against the derivation of the 
stone layers, though more elaborate, of the Cycadean seed from the hard 
shell of Lagenostoma. 
Perhaps there is по more obvious, and at the same time interesting, 
question with regard to palæozoic seeds than the method of pollination, even 
if any attempts at an answer must for ever remain within the region of 
hypothesis. In the case under consideration, it seems very possible that 
the well-marked apical ridges were concerned in pollination, since no other 
organ, such as cone-scale, bract, or earpel, to aid in this function is known. 
They may conceivably have acted as the stigmatic rays of a poppy capsule, 
or the lines on the petals of a pansy, are supposed to do ; but as it is scarcely 
certain that such lines are attractive to ог guide insects in recent plants, 
and even less certain *. that pollination of these seeds was effected by insects 
at all, this cannot be further pursued. But it seems to me possible that 
they, or rather the grooves they formed between them, promoted pollination 
in another way. Long ago Oliver showed (13, p. 461) that, “compared 
with the ordinary palæozoic type of seed, Lagenostoma seems peculiar in the 
lack of tracheal supply beneath its pollen-ehamber? ; and this statement is 
strikingly illustrated. by the plate accompanying the paper (pl. 24), where 
the vascular system is seen in all the different seeds, recent or fossil, to 
approach the pollen-chamber except in Layenostoma. The detailed ex- 
amination of numerous specimens, many very well preserved, of two different 
species, permits us to reject the possibility that this deficiency is due to 
imperfect preservation; and if we also reject the hypothesis of the 
hydathodes and porous integument (р. 474), ах there’ seems no structural 
* See, however, Oliver and Scott, (16) p. 214. 
