501. 
of the lowermost portion of the frond issuing from the disc shows a marked differ- 
ence between the frond and the disc. In the neighbourhood the cell-rows of the 
disc are bent outwards, the cell-walls, which in 
the normal dise are firm, swell, the intercellular 
substance becoming much developed and gelatinous, 
and numerous transverse secondary pits appear 
between the cells of the originally vertical cell- 
rows (Fig. 460). These cell-rows gradually pass 
into the cortical cell-rows of the upright shoot, 
where the transverse secondary pits are also 
numerous and very long. These secondary pits 
enable a more intense longitudinal conductive 
power between the frond and the disc. 
The structure of the upright frond has 
repeatedly been described and pictured (Kürzıng 
1843, WILLE, DARBISHIRE, OLTMANNS, KyLın 1923). 
The tip of the frond has the structure designed 
by OLTManns as the fountain type (Springbrunnen- 
typus) (Kyrın 1823, p. 20, fig. 10 a). The medullar 
or conducting tissue is built up of elongated cells 
arranged in longitudinal rows, 7—16 x in inner 
diameter, connected with small pits in the end- 
walls and here and there also by transverse pils 
of secondary origin. The longitudinal cell-rows Fig. 460. 
may be more or less bent, especially in the older ee 
parts of the frond. WILLE (1887, p. 83) thought shoot; the latter issued to the right. 350: 1. 
that this might be explained by the supposition 
that the ends of the long cells slide past each other much as the bast-cells of 
the Phanerogams. This view, however, cannot be upheld, for the ends of these cells 
are connected by (primary) pits which persist 
and do not permit of such a sliding growth. The 
cells of the outer longitudinal cell-rows are much 
shorter than the inner ones, and gradually pass 
into the cortical layer which consists of branched 
cell-rows that are outward-directed and not 
unfrequently connected with secondary pits. The 
inner part of these cell-rows forms the storage 
Fig. 461. tissue. The last 2 or 3 cells in the cortical cell- 
Chondrus crispus- Vertical section of the cortex rows are very narrow and contain no starch, 
at the base of an upright shoot. 560: 1. : 
whereas the inner cells are more or less filled 
with starch-grains. For further details of the anatomy and cytology see the authors 
quoted, in particular DARBISHIRE. According to this author each cell contains only 
