2 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 26 



1095-1645, Apr. 1946; 1646-1989, May 1946; 2005-2165, June 1946; 

 2498a-2673 (W. Williams) Apr.-May 1946; 2756-3145, Oct. 1946; 

 3146-3581, Nov. 1946; 3582-3764, Dec. 1946; 3765-3940, Jan.-Feb. 

 1947; 3942-3976, 3982-4040, 4099-4113 (C. L. Hubbs & E. Flynn) 

 Aug. 1946; 4041-4098, 4114-4162 (C. L. Hubbs) Dec. 1946; 5143-5312 

 Sept. 1948; 6462-7278, 7795-7810 Mar. 1949; 8124-8917, Dec. 1949 

 Jan. 1950; 9044-9554, Apr.-May 1950; 9624-10095, Apr. 1951; 10279 

 10288, Aug. 1951; 10289-10589, Oct.-Nov. 1951; 10672-10691, Dec 

 1951; 10742-11040, May-June 1952; 12036-12176, Nov. 1953; 12239 

 12247, Apr. 1954; 12248-12542, Jan.-Feb. 1954; 13228-13606, Apr 

 1955; 18545-18988, Apr. 1958 (first set in Herb. Los Angeles County 

 Museum); 19191-19200 (K. Norris) Sept. 1952; 19201-19224 (K. 

 Norris) Mar.-Apr. 1952; 19225-19286 (C. L. Hubbs) Oct.-Dec. 1957; 

 19287-19306 (C. L. Hubbs) Nov. 1954; 20154-20632, 20804-20949 

 (M. Neushul) Aug. 1957; 20991-21500, Apr. 1959; 21501-21536 

 (E. S. Reese) Aug. 1959; 21686-21753, Nov. 1960. 



The photographs are the work of Don Ollis of Santa Barbara. 

 The Latin diagnoses were kindly prepared by Dr. Hannah Croasdale. 

 Thanks are also due to Miss Florence Ralph and Dr. Clinton Dawes for 

 assistance in the research. 



Ceramiaceae 



Key to the Genera in the Pacific Mexican Flora 



1. Thallus consisting of spongy, flabellate blades Haloplegma 



1. Thallus not spongy, without definitive blades 2 



2. Final orders of branches or all branches uncorticated 8 



2. Final orders of branches incompletely or completely corti- 

 cated 3 



3. Cortication of branches differentiated into nodes and internodes 4 



3. Cortication homogeneous from base to apex of branch 6 



4. Corticating cells rectangular and in vertical rows 



Centroceras 



4. Corticating cells polygonal and irregularly arranged 5 



5. All axes and branches corticated similarly .. Ceramium (in part) 

 5. Main axes fully corticated; ultimate branchlets corticated only 



by bands Spyridia 



6. Branching distichous 7 



6. Branching not distichous Ceramium (in part) 



7. Branching opposite and the two opposite branches unlike 8 



7. Branching alternate or pectinate Microcladia 



8. Leaf-like branchlets smooth on one or both sides, of limited 



growth, not growing out into branches Neoptilota 



8. Leaf-like branchlets serrate on both sides, not necessarily 

 of limited growth, often growing out into branches .... Ptilota 



