CYTOLOGY AND SYSTEMATIC POSITION OF PORPHYRIDIUM 
CRUENTUM NAEGELI 
IvEY F. Lewis and Conway Zirkle 
Porphyridium cruenttim, named by Nageli in 1849, has had a systematic 
history equaled by few plants. It had previously been called at various 
times Thelepora, Tremella, Sarcoderma, and Byssus. Agardh (cit. Brand) 
named it Palmella cruenta, and under t^his name Hassall classified it with 
the Palmellaceae. Indeed, Nageli himself placed it in this group, and 
there it was kept by Ktitzing in his Tabulae Phycologicae (1849-71) under 
the name given it by Agardh. Rabenhorst seems to have been the first 
to place it in the Porphyraceae (1868), and he was followed in this four 
years later by Wood. Cooke in 1884 returned it to the Palmellaceae. 
Wolle likewise placed Porphyridium in the Chlorophyceae and found it to 
be identical with Protococcus miniatus. On the other hand, Schmitz (cit. 
Brand) considered it related to the Florideae, and Gaidukov (cit. Engler 
and Prantl) put it in the Bangiaceae. In 1902 Chodat returned it to the 
Chlorophyceae and would place it near Schizogonium. West two years 
later believed that Porphyridium belongs in the Myxophyceae and is allied 
to Aphanocapsa, while Hansgirg (cit. DeToni) made the genus but a species 
of Aphanocapsa and called it A. cruenta. Oltmanns in 1905 put Porphyri- 
dium once more in the Chlorophyceae. He was not certain as to its exact 
position but placed it supplementary to the Scenedesmaceae. DeToni 
classified Porphyridium as one of the Myxophyceae belonging to the family 
Glaucophyceae. Brand in 1908, as a result of his work on this plant, 
believed that it belongs to the Bangiaceae, and in this he is generally followed 
by the systematists, Engler and Prantl, West, who changes his original 
position, and Collins. Tilden, however, keeps Porphyridium in the Myxo- 
phyceae. While Kufferath got some results very different from Brand's, 
he agreed with the latter as to its systematic position, although he sug- 
gested that in the contingency of its having no chlorophyll it be placed 
with the red bacteria. Brand cited Borzi as being in favor of putting 
Porphyridium with Protococcus, Richter as favoring putting it with 
Trentepohlia, while Klebs would have it as a questionable member of 
the Pleurococcaceae. 
The descriptions of Porphyridium differ almost as much as its various 
systematic positions. Nageli, working unfortunately with dried material, 
described it as follows: 
"Cells flattened, in surface view round or somewhat polygonal from 
lateral pressure, with a lateral thin confluent sheath, united in one-layered 
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