DEVELOPMENT OF CONCEPTACLE IN THE 1’UCACE.E. 41 
Besides the division shown in fig. 4, the basal cell at this 
time divides also in two planes at right angles to this and to 
one another, giving rise to a group of eight cells, four of 
which only can be seen at once in a section (fig. 5). These 
cells, during the further development of the conceptacle, 
appear to differ functionally in no respect from the other 
tissues bordering on the cavity. These tissues, having 
increased principally by divisions at right angles to the 
inner surface of the conceptacle, form a layer of thin w'alled, 
closely compressed, protoplasmic cells, which completely line 
the cavity; by these peculiarities this tissue is pretty sharply 
marked off from the adjacent cortical tissue. 
Coincident with this increase in number of the constituents 
of the lining tissue is a change in form of the whole con- 
ceptacle. The low-er part of the cavity becomes wider, so 
that the whole conceptacle assumes a flask form, which may 
be recognised in fig. 5, but becomes more pronounced at the 
stage represented in fig. 6.^ 
In the stage represented in fig. 6 the central column may 
often be found, still continuous, from the point, where the 
initial cell is fixed, to the neck of the conceptacle, which is, 
however, still closed. The column shows a jagged irregular 
outline, owing to the rupture of the strings which originally 
connected it (as in fig. 5) with the walls of the conceptacle. 
It may be noticed that the margin of the cavity is still 
unbroken by any outgrowth of hairs. 
which is then seen to be continuous witli the outer portion of the thickened 
covering of the limiting tissue, this we have designated c. 
The conclusions to be drawn from these observations are, that 'a is a 
swollen form of cell-w'all, which is not true cellulose, but is similar to the 
central portion of older cell-w'alls of the tissue of the larger tangles 
(“Innenlamelle,” Luerssen, p. 101 ; ‘"Gelin” (?), Kiitzing, ‘Phyc. Gen.,’ 
p. 31). That 6 is a substance coincident with mucilage (“ Schleim,” 
Kiitzing, ‘ Phyc. Gen.,’ p. 30) ; that is a substance akin to cuticle. 
^ It seems to me probable that the power of swelling with water possessed 
by tlie mucilaginous contents of the conceptacle, and the consequent internal 
pressure exercised on the internal surface of the conceptacle, has some con- 
nection with this form. Suppose such an internal pressure. The concep- 
tacle is completely closed. If a yielding occurs it will naturally be at the 
point where the resistance is least, and that will be where the tissues are 
least crowded. This is, however, the case in the interior of the lhallus. 
The cavity will then enlarge most at its base. Hence the flask shape. 
This explanation is further supported by the fact that where the curva- 
ture is greatest (and the form of the conceptacle is usually less regular than 
in our fig. G) there the cells of the lining tissue are largest. Hence it may 
be concluded, other things being equal, that there the external resistance 
was least. This supports our view. Again, it is universally the case that 
around the mouth of a conceptacle the surface of tlie thallus is raised so 
as to form a slight liillock (cf. figs. C, 7). This would naturally be the 
result if an internal tension existed 
