Holtz: OBSERVATIONS ON PELVETIA. 29 
shape as the outer cells of the cortex are approached. Here 
they appear to be simply the original dividing wall. They can, 
however, be located by the protoplasm apparently running right 
through the wall at these places. This apparent communica- 
tion of the protoplasm of adjoining cells was observed as far out 
as the second layer of cells below the epidermis. Farther out 
‘this could not be seen on account of the chromatophores. But 
probably even the epidermal cells communicate with each other. 
The concentrated sulphuric acid test showed that the plates 
were dissolved as well as the rest of the wall. No positive 
proof was found that the pits were perforated, no threads of 
protoplasm having been observed, as would indeed be difficult 
with the extreme thinness of the plates. But the symmetrical 
arrangement or attachment of the protoplasm on both sides of 
the pits leads one to suspect very strongly that there is com- 
munication. By plasmolysis the protoplasm draws away from 
the cell wall at all other points than the pits (/7g. 73). It 
remains attached here and extends in ropes through the cells 
and seemingly through the pits. The protoplasm often branches 
to lateral pits (/7g. zz). When the pith cells are swollen in 
fresh water the protoplasm is frequently torn off from one end 
of the cell, away from a pit, owing apparently to the elongation 
of the lateral wall as well as the gelatinous matrix. In such 
cases the pit curves in toward the loosened protoplasm (/7gs. 
W251 14). 
Iodine is the most satisfactory stain to use in studying pits. 
The protoplasm is stained and its attachments may be studied. 
Pits and anastomosis may be nicely studied by removing some 
of the protruding pith from a lamina that has burst in fresh 
water. By flattening the gelatinous mass under the cover glass 
the pith cells and their pits show up well, even unstained, though 
better if differentiated with stains for walls and for protoplasm. 
Anatomy of Foldfast, Stipe and Lamina. —'The above mat- 
ter on the tissues in the body of P. fast7gvata needs some modi- 
fication and addition when the holdfast, stipe and lamina are 
considered separately. 
Floldfast. —In a vertical section through a holdfast it is seen 
to be composed of approximately regular, ascending rows of 
cells; those near the central part more vertical; those near the 
border of the holdfast curving out as they go down. ‘There is 
a marked difference: between the cells in the middle and those 
