44 Thoday . — Anatomy of the Ovule and Seed in 
epidermis. A short way down (Photo 8, PL I) the free portion of the 
upwardly projecting flange is cut (see Af Text-figs, a and 3), its inner 
edge fringed by crushed rows of cells with corky walls ; growth from a cork 
cambium has occurred, cutting off dead and empty cork-cells over the 
exposed free region of the flange, and thus protecting the delicate tissues 
beneath. Photo 9, PL I, is from a section below the free flange, and shows 
the base of the cork cambium at the junction of the micropylar tube and 
the flange. The lumen of the tube is narrowed by the subdivision of the 
epidermal layer, while the outer surface of the proliferated wall is fused with 
the outer covering, and the boundary between them ( e , Photo 9) is not 
readily distinguishable; in Photos 10 and 11 the inner epidermis of the 
outer covering is clearly marked, though the surface of the tube, as a con- 
sequence of the growth in thickness of its wall (now composed of 20 or more 
layers of cells), is firmly pressed against the outer covering and is fused 
with it. From here downwards to the bottom of the flange the limits of the 
two are often quite indistinguishable, though at intervals irregular cracks 
appear, filled with a mucilaginous substance. In Photo 10, PL I, the lumen 
of the micropylar tube has entirely disappeared, though its original position 
is still marked by two or more thick-walled cells which used to form part 
of its lining. This solid portion of the tube, sometimes, but not always, 
having a little strand of thick-walled cells in the centre, is continuous for 
some distance (see Text-figs. 2 D and 3). 
About two-thirds of the way down the wide region of the tube the 
strand of thick-walled cells becomes more prominent, and an opening 
reappears among them filled, however, by a solid mass of large cells with 
their walls heavily cuticularized, irregularly orientated, and looking like 
thyloses or papillae cut at intervals (Photo 11, PL I). These are, of 
course, the papillae described before, 1 which grew out from the epidermal 
cells of the lining. The wall outside the solid mass is composed of fewer 
layers, so that it would appear that there has been much less activity of 
the outer layers of the tube wall ; as a consequence, the lumen in this 
region has not been closed by external pressure but by the ingrowth of 
papillae. 
The papillate region is very short ; the papillae suddenly become torn 
and few in number, and the whole middle of the tube next disappears, having, 
as was seen in the longitudinal section, been broken across and torn out. In 
Photo 12 there is consequently a large open, often mucilaginous cavity (g), 
irregularly lined by torn cells and bounded by a few layers of cells firmly 
fused to the outer covering. 
Photo 13. PL I, 2 passes through the sudden enlargement of the outer 
layers of the micropylar tube to form the downwardly directed flange (Bf) 
which in the young seed projects over the tip of the middle covering 
p. 7. 2 N.B. Photos 13 and. 14 are on a smaller scale than the others of this series. 
1 
