Lewis. — The Life History of Grijfithsici Bornetiana. 643 
A typical intercellular connexion is shown in Fig. 6. The pore in the 
cross-walls is closed on each side by a disk, which is the ‘ stopper/ or ‘ plug ’ 
of Archer (8). This disk is in direct contact with the thickened pad of 
cytoplasm lying on the cross-wall. Connecting the disks is a broad strand 
of thin clear cytoplasm, or, in some cases, several smaller strands (Fig. 8). 
In several instances, bits of the proteid substance normally present in the 
pad have been found in the cytoplasmic strand which connects neighbouring 
disks, apparently having been fixed in transit from one cell to another 
(Fig. 6). The middle lamella mentioned later as being formed in some 
cases in cell-divisions has not been demonstrated in the older inter- 
cellular connexions. 
The size of the pore varies with the size of the cells which it connects. 
The average diameter of the disks, which is the same as that of the pores, is 
about 1 1 /x in the large cells at some distance from the apex. 
In living and in unstained fixed material the disks are refractive 
colourless bodies. They stain heavily with nuclear dyes, particularly with 
Heidenhain’s haematoxylin. Cytoplasmic stains, such as eosin, colour them 
much less intensely. They are soluble in Javelle water, as was pointed out 
by Kienitz-Gerloff (46). This fact, coupled with the fact that the disks are 
continuous on both sides with unaltered cytoplasm, gives support to the 
view, first expressed by Schmitz (70) that they are protoplasmic in nature. 
The results obtained by various workers on intercellular connexions in 
the red algae are conflicting. Archer (3) described in Ballia pits which 
were at first open and later became closed by a plug, or ‘ stopper/ Schmitz 
(70) came to the conclusion that the pit is closed by a delicate membrane, 
which is pierced by many or several protoplasmic strands. Hick (42) 
thought he had demonstrated a simple protoplasmic strand passing through 
the open pit. Moore (55) found that a pit-closing membrane is pierced by 
one or several protoplasmic strands. Wille (88) described and figured a 
sort of sieve tube in Cystocloninm. Harvey-Gibson (39) found that in 
Polysiphonia fastigiata an actual protoplasmic connexion is present only in 
young stages and that later a plug closes the pore-canal. However, he 
mentions that from the edges of the plug fibrillar thickenings connect the 
neighbouring protoplasts. Kohl (49) regarded the matter of protoplasmic 
continuity in the Florideae as still unsettled. Kienitz-Gerloff (46) found 
that the pit is closed by a delicate membrane, and reached the conclusion 
that an unbroken connexion cannot be said with certainty to exist in the 
form studied ( Polysiphonia ). 
The number of nuclei in a single vegetative cell is always large. Since 
the nuclei are approximately equidistant in each cell below the apex, it is 
evident that the number in a cell varies directly with the size of the cell. 
Estimates made from several preparations show that the large cells near 
the base of the plant contain, on an average, 3,000-4,000 nuclei. As the 
X x 
