392 University of California Publications in Botany [Vol. 6 



and Kjellman removed the species to that genus in 1883. Rupreeht, 

 in discussing the relation of C. Middendorfjii to C. pellita, says that 

 the former has a much more highly developed basal tissue. 



Kjellman in discussing a Petrocelis from the Arctic Sea states 

 that he thinks it conforms to the description of the Ochotsk plant of 

 Rupreeht, agreeing with him in his opinion as regards the difference 

 between the Ochotsk plant and the European Curoria pellita, and 

 thus places the Arctic Sea plant under P. MiddendorffH, stating that 

 it differs from P. cruenta in having "a more strongly developed basal 

 layer, by the vertical cell-rows being often branched, and, above all, 

 by the different shape and position of the tetrasporangia. " 



I have examined a portion of the Arctic Sea plant in the Her- 

 barium of the University of California from northern Norway marked 

 C. Middendorfjii by Kjellman, and the vegetative characters seem to 

 agree with those of the Ochotsk plant as described by Rupreeht. 

 The specimen, however, is sterile, and nothing can here be said defi- 

 niteh^ concerning the identify of the Arctic Sea specimen and the 

 Ochotsk plant. Our Pacific Coast plant does not agree in structure 

 with the Arctic Sea plant, and judging from the descriptions alone, 

 as no specimens of the Ochotsk plants are available, our plant is 

 sufficiently different from that to warrant a new description and 

 new name. 



Usually about one-fourth of the thallus of P. franciscana consists 

 of a compact mass of cells which in the growing region around the 

 margin are somewhat parenchymatous and which may remain so for 

 some time in certain parts of the thallus, but which later increase 

 considerably in size and join with each other profusely by short lateral 

 projections of the protoplasts. The basal layer gives rise to the per- 

 pendicular filaments whose cells have thick gelatinous walls. Repro- 

 duction as at present known is wholl}^ by intercalary tetrasporangia 

 formed by the direct transformation of vegetative cells, one in a 

 filament usually, with cruciate tetraspores. The tetrasporangia are 

 20-28/x, wide, and up to 40/i, long. These grow in great abundance 

 in a zone usually about twenty-five cells from the outer surface. 

 The tetrasporangial zone is about fifteen cells wide, one tetraspo- 

 rangium in a filament but not all developing at the same level. There 

 is considerable difference in the shape of the tetrasporangia. Age 

 seems to be one of the governing factors in this respect. The first 

 indication of their formation is seen to be the enlargement of a cell 

 usually of equal dimensions. The cell remains square in section for 



