NO. 1 DAWSON: MARINE RED ALGAE OF PACIFIC MEXICO 75 



completely so below. D. 9670, 9701, outer peninsula at Bahia San 

 Quintin; D. 1147, 8907, Punta Baja; D. 8701, Bahia Rosario. 



Ptilota filicina (Farl.) J. Ag. 

 PL 33, fig. 3-4 

 J. Agardh 1876, p. 76; Dawson 1949, p. 220. Ptilota plumosa var. filicina 

 Farlow 1875, p. 374. 



Thalli usually 10-35 cm. tall, bright red, with several long branches 

 and these with 2-4 orders of branching; branches with leaflets and un- 

 branched branches in opposite pairs and regularly alternate; leaflets 

 slightly falcate, with both margins serrate, the tips acute; branches 

 opposite the leaflets frequently 2-5 cm. long and with well-developed 

 leaflets; tetrasporangia elliptical, about 65 jx long, scattered among 

 branchlets in special branches from adaxial margin of leaflets, these 

 tufted, multifarious, of incurved, mostly uniseriate short filaments; 

 cystocarps borne on ultimate branchlets, modifying them to appear as 

 shortly-pedicellate, tufted bodies about 500 /x in diam. consisting of a 

 spherical gonimoblast surrounded by a clasping involucre of short fila- 

 ments. 



Type: A collection by Capt. Pike, labeled "Ptilota calif ornica var. 

 concinna" in Herb. Harvey, Trinity College, Dublin. 



Type locality : Golden Gate [San Francisco], California. 



Mexican distribution: Pacific Baja Calif. — D. 5156, Cabo 

 Colnett; D. 124, Rio San Telmo; D. 8734, 9683, outer peninsula of 

 Bahia San Quintin; D. 8906 Punta Baja. 



DELESSERIACEAE 

 Key to the Genera in the Mexican Flora 



1. Apex with horizontally divided primary apical cell 2 



1. Apex without a horizontally divided primary apical cell 16 



2. Intercalary divisions absent in cell rows of the first order 3 

 2. Intercalary divisions present in cell rows of the first order 9 



3. All tertiary apical cells reaching the thallus margin 4 



3. Not all tertiary apical cells reaching the thallus margin 5 



4. Thallus branching from the margins Branchioglossum 



4. Thallus branching from the midrib Hypoglossum 



5. Intercalary cell divisions lacking 6 



5. Intercalary cell divisions in the cell rows of the second and 



higher orders present Grinnellia 



6. Blades ligulate, narrow, less than 300 }i wide 8 



6. Blades not ligulate, broader, 2 mm. to 3-4 cm. wide 7 



7. Thallus with polystromatic midrib and monostromatic mar- 

 ginal parts Membranoptera 



7. Thallus polystromatic throughout; reproduction in special 

 small leaflets Holmesia 



WOODS 



