1917] Gardner: New Pacific Coast Marine Algae I 393 



some time, and then begins to enlarge, in some instances becoming 

 spherical and in others narrowl}^ ellipsoidal. Plants with these 

 differences may be found growing close together on a rock, or different 

 parts of the same specimen may possess them. I have not been able 

 to discover any other constant difference to accompanj- this difference 

 in size of tetrasporangia and hence am unable to separate species on 

 spore characters alone. 



Plants fruit during the months of December, January, and Feb- 

 ruary. By the last of March practically all of the spores have been 

 shed and all of the tissue from the sporangial zone has sloughed off. 

 Prior to tiiis time many of the cells in a zone just beneath the fruiting 

 zone have anastomosed b}- sending out short tubes, thus binding the 

 filaments together. Then the outer part of the thallus is regenerated 

 by branches from some of the cells in the anastomosing zone. Thus 

 the species is perennial, but the length of time the individual may 

 persist has not been determined. Its chief competitor for rock area 

 in this vicinity is the genus HildeiibrandUa. Petrocelis seems gen- 

 erally to override it. 



In some instances in which the plants are abundant it is not an 

 easy matter to determine the limits of the individuals since they 

 become confluent, but individual plants have been observed that are 

 ten inches across, and doubtless many may attain a much greater 

 expansion. I have observed rock areas of many square feet com- 

 pletely covered by the plant. 



P. franciscana differs from P. Middendorffii in having anastomos- 

 ing cells at the base and in zones in the erect filaments, in having 

 larger tetrasporangia. up to 28/i wide, while those of P. Middendorffii 

 are but 9-9. 5ju, wide, and in Ix'ing nuieh larger in every way. 



Hildenbrandtia occidentalis Setchell sp. nov. 

 Plate 33, fig. 4 



Thallo saxicola, tenaciter adhaerenti, 1-2 mm. crasso, indefinite 

 expanso, saturate puvpureo rubro, siecitate in saxis nigro. filamentis 

 minutis, compactis, ])arallelis et substrato perpeiulieularibus oompo- 

 sito, firmo baud gelatinoso; cellulis filamentorum 3-4. Oju diam., quad- 

 ratis aut 2-3 plo quam diametro longioribus; ])arietibus cellularum 

 tenuibus firmisciue ; conceptaculis lunnei'osis in thallo conspersis, 

 cylindrieis, 200-300/i, profundis, ampullaeformibus, ad faucem con- 

 strictis, 100-150/i, latis ; tetrasporangiis zonatis 25-32/* longis, 9-10/i, 

 latis ; parietibus tenuibus ad parietes internos conceptaculorum per- 

 pendicularibus ; paraphysibus nullis. 



