14 Oliver and Salisbury . — On the Structure and 
(‘ lip *) surrounding the glands of Polygonum , &c., and may even have 
served a similar purpose. 1 
Lining the micropyle and continuous with this soft tissue was a single 
layer of cells, of which only the membrane forming the micropylar tube 
is preserved (R. m, PI. I, Fig. 7, m.m .). This latter consists of several 
tiers of longitudinally elongated elements, which here and there show faint 
spiral markings ; the cells of each tier are of approximately equal length, 
and, in the middle region, stand directly above those of the tier below. 
In width they were nearly the same throughout (17 f), the increased cir- 
cumference of the micropyle at the base entailing a corresponding increase 
in their number. At the level of the lagenostome this lining layer of 
cells suddenly thickened to form a triangular flange, which rested on the 
upper edge of that organ. A similar flange occupied the shallow sinus 
where the lagenostome rested upon the plinth. In section the flanges 
appear as angular projections into the micropyle (R. 117, PI. II, Fig. 18, 
uf. and If). Below the lagenostome the membrane closely ensheathed 
the dome-shaped plinth, at the base of which the nucellus and integu- 
ment become fused. In two of the sections the sinus between this mem- 
brane and the plinth is seen cut across at the base (R. 11c, PI. II, 
Fig. 14, ^., and R. 117, PI. II, Fig. 16, s). Below this point the nucellus 
and testa were connected by soft-celled tissue, through which the vascular 
bundles passed. In section R. 114 (PL I, Fig. 2, pl.j) the single layer 
of cells forming the lining membrane of the micropyle is seen cut across 
between the flanges. From this we see that the lagenostome and plinth, 
although free, were closely ensheathed by the integumental membrane, 
which by means of the flanges held the lagenostome in a tightly fitting 
socket, thus ensuring perfect continuity between the passage of the micro- 
pyle and the cavity of the lagenostome; to such an extent was this the 
case that the contraction of the nucellus previous to fossilization, which 
usually takes place, has not only caused the lagenostome to descend, 
but has in some cases brought down the micropylar tube with it, caus- 
ing rupture near the apex (R. 111, PI. I, Fig. 7). So long as these were 
the only sections available, the tube appeared to belong to the lageno- 
stome, but the sections which have more recently come to hand show clearly 
that its true nature is integumental (Watson’s 268, PI. II, Fig. 12, m.m., 
and R. 123, PI. II, Fig. 19, inf), as the continuity with the soft tissue 
at the apex is completely shown. 
6. The 1 Blow- off ’ L ayer. 
Investing the whole external surface of the seed was a differentiated 
epidermis, which we shall term the ‘ blow-off ’ layer. This, together with 
1 E. J. Salisbury : On the Extrafloral Nectaries of the Genus Polygonum. Ann. of Bot., 
vol. xxiii, 1909, p. 239. 
