334 
IVEY F. LEWIS AND CONWAY ZIRKLE 
free-lying families; divisions in varying vertical planes; all generations 
fully developed and alike; cell contents purple. 
''Type P. cruentum {Palmella omenta Ag.), the only known species. 
''The blood-red gelatinous layer consists of larger or smaller one- 
layered plates, whose cells seen from the surface appear rounded and 
mostly somewhat angular. The thickness of the cells is in dry specimens 
one third to one fifth the breadth. The thin sheaths run together in a 
structureless jelly in which the cells are imbedded. The sheaths are one 
third to one fifth, more seldom up to one half, of the lumen. The true wall 
is very thin. 
"The cell content is colored by erythrophyll. It looks beautifully 
purple and agrees in color with Porphyra vulgaris. I could not see a nucleus 
in it." 
On procuring some living material he amended his description somewhat: 
"Cells spherical or polyhedric with tolerably thin confluent sheaths, 
united in a somewhat gelatinous layer; divisions varying in all directions 
of space or exceptionally only in vertical planes. . . . This genus is dis- 
tinguished from Palmella by the erythrophyll in the cell content." He 
added in a note: "Further I saw in the fresh plant, often in every cell, a 
whitish granule (a chromatophore filling itself with starch), such as the 
other Palmellaceae possess." 
In 1875 Mer found starch in Porphyridium, and in the same year 
Saint-Leon found no trace of sexual reproduction and only simple multiplica- 
tion through the division of the vegetative cells. Schnetzler (1878) reported 
that the red coloring matter disappears when the alga is pickled in a borax 
solution, leaving the color green, and Nebelung (1878) that the red pigment 
has a spectrum which may be considered as a modified spectrum of the 
pigment of Phormidium. Schmitz added considerably to our knowledge 
of this alga by describing in it a star-shaped chromatophore, which, like 
those of the Bangiaceae, Bacillariaceae, and Rhodophyceae, contains no 
starch; and also a colorless centrally located pyrenoid and an eccentric 
nucleus. Later he reported that "the special cell membrane is repeatedly 
formed anew on the single cells, the old membrane is torn through on one 
side and stripped ofT as a stalk, at first sharply delineated and later becoming 
more and more formless gelatin." On the other hand, Oltmanns described 
the cells as being imbedded in formless jelly. 
Brand reported that the chromatophore is not typically star-shaped but 
often in wet weather is round, and that the star-shape, when it does occur, 
comes from its being indented with the peripherally located granules and 
vacuoles. These granules he took to be cyanophycin granules, though he 
records that they are not stainable with acid carmin, which is generally 
held to be the most typical stain for such granules. The coloring matter, 
he found, is floridean red and varies only in its intensity. He was unable to 
find any green modification. The pyrenoid is described as being ring-shaped 
