264. PROF. F. W. OLIVER ON THE STRUCTURE 
continuous mantle of spiral or scalariform tracheides. ‘This mantle runs just below the 
epidermis of the nucellus, and reaches right up to the top of the macrospore. Here the 
tracheides pass into the lower region or extension of the pollen-chamber, paving its floor 
and lining its sides, but never penetrating to the upper portion or pollen-chamber proper. 
In the region of the pollen-chamber the lateral tissue of the nucellus is often preserved, 
forming an S-shaped pad of thin-walled, spindle-shaped cells right and left of the obtuse 
tapering apex (as seen in a median longitudinal section, e.g. in fig. 2, sh.). This 
tissue, however, dies out before the canal connecting the pollen-chamber and micropyle 
is reached. 
At the junction of the nucellus and the narrow canal just mentioned there occurs 
almost invariably what at first sight appears to be a sort of collar folded down over the 
top of the nucellus like a small inverted funnel (Pl. 41. figs. 3 & 1 å, co.). The structure 
is very puzzling in all sections not ground to their ultimate fineness. It forms a 
characteristic feature in the Brongniartian drawings * like a pair of backwardly-directed 
antennse, but no direct reference is made to it in the literature. 
The macrospore is limited by a well-defined and fairly thick membrane in contact 
laterally with the attenuated residue of the nucellus; but at the apex always, and at the 
base frequently, it has undergone considerable contraction, so that in these regions it no 
longer follows the contour of the nucellus. In the living seed the base of the macrospore, 
no doubt, fitted on to the chalazal tissues; whilst at the apex it was convex, encroaching 
considerably upon what is loosely termed the pollen-chamber. 
As regards the contents of the macrospore I have nothing to add to what is shown in 
Brongniart's figures. A prothallium more or less contracted from the wall is usually 
preserved (PL 41. fig. 3, pr.), and in lucky sections archegonia are found below the pollen- 
chamber (fig. 3, ar.). These seem to have been present to the number of two; and if 
this be really the case, the gametophyte alone in this seed exhibits bilateral rather than 
radial symmetry. But I was unable to settle this point by a critical section, such 
horizontal sections as have been obtained through this region being ill-served as regards 
the preservation of the prothallium. ‘Though the egg-cell, which was large, and what is 
perhaps its nucleus, often shows as a striking cytological object (Pl. 41. fig. 3, ar.), no 
details of morphological value are recognisable. 
Above is given in brief outline a general account of the more obvious featurcs of the 
seed. I now pass on to speak in fuller detail of certain regions. 
The Testa and the Chalaza. 
Except at the chalaza and at the apex of the seed the sclerotesta has a uniform 
structure and thickness (33 mm.). Externally thereis a palisade-layer (Pl. 41. fig. 4, p-), 
in height about half the diameter of the sclerotesta. This layer is supported by a zone 
of short thick cells, whilst below these are several layers of fibres ( f.) which run in the 
longitudinal direction. As a lining to the sclerotesta we find a well-marked layer of 
fairly large flattened cells with carbonised contents and clear refringent walls (e£.). This 
* * Graines fossiles,’ pl. 16. figs. 5, 8, &c. 
