70 
erigilur et fil fere cucullatim involuta, marginibus sursum hiantibus (1. c. fig. 42)”. 
The celebrated author has not perceived that the leaf-like frond arises by splitting 
of a globular vesicle, but his fig. 41 seems to represent just the state where the 
split is formed. When the frond grows older, numerous rhizines are formed from 
the cells in the lowest part of the frond, which may result in the original basal 
cushion becoming less distinct; it is however always evident that the cells in the 
basal portion of the frond are situated in more than one plane. 
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Porphyropsis coccinea. A, young plant. still hemispherical. 550-1. B. more developed plant with expanded 
lamina and spore-mother cells scattered over the frond. 340:1. C. lower part of older plant: it was not 
plane. but the borders were curved somewhat backwards. 340:1. D, basal portion of frond showing the 
rhizines. 550:1. 
This plant offers an interesting analogy to the genus Monostroma among the 
Chlorophycee and the genus Omphalophyllum among the Phæophyceæ. In Porphyra 
naiadum Anderson the frond also begins according to Hus (1902, p. 212) as a 
parenchymatous cushion, but the later development is quite different from the 
above described, the cushion producing from its surface hair-like projections which, 
dividing in two directions, give rise to a monostromatic frond. 
The cell-divisions take place in some measure uniformly over the whole 
