432 
IOWA ACADEMY OF SCIENCE Vol. XXIV, 1917 
A weak eosin solution was used to test the conducting power 
of these cells, but the experiments were not wholly satisfactory 
as the whole thallus took the stain. There was a marked dif- 
ference in the degree to which the strand stained, as they be- 
came much darker than the surrounding cells. But even this 
would seem to indicate that more of the fluid was retained in 
the strands than in the remainder of the thallus. 
Generally, only two strands were found in a single thallus 
but the number varies from, two to five, depending on the 
amount of branching. They are found laterally in the thickened 
midrib of Blasia about equidistant between the dorsal and ven- 
tral surfaces. Where the thallus branched the strand divided 
giving off branches to each newly formed division. The angles 
of the cell walls were quite sharp in the transverse section but 
other markings were not found here (2, figure 84). 
In the longitudinal section (3, figure 85) a greater difference 
was noticeable. The conducting cells, averaging the same in width 
as those of the thallus, had a length three to five times greater 
and tapered to a point at each end. Cross Avails in some speci- 
mens run obliquely through these long tubes. The most strik- 
ing characteristic Avas the peculiar markings of the cell walls. 
The pits or depressions arranged irregularly along the walls 
are thin at the center and bordered by heavy darkly staining 
thickenings, giving the external appearance shown in 4, figure 
85. These thickenings sIioav at fairly regular intervals along 
the wall in the prepared sections. Where the strands join the 
spongy tissue on either side, only the inside walls bear the mark- 
ings. The strands undoubtedly serve in a mechanical capacity, 
being provided with such strong Avails, but it is doubtful if this 
is their most important function. It does not seem consistent, 
that a tlialloid liverwort, attached by rhizoids for three-fourths 
its length, would need such strengthening as the strands might 
give. HoAvever, it is possible in the case of Blasia pusilla , that 
the resistant cells aid in giving body to the thallus upon which 
are found the gemmae receptacles and large sporophytes. Gottsche 
found that in Symphyogyna they had no connection with the 
“receptacles” on which the sexual organs were seated. 
These strand cells do not show nuclei, but simply a disinteg- 
rated substance, probably protoplasm, as it took the stain as 
readily and to about the same degree as the protoplasm in the 
surrounding cells. 
