510 University of California Publications in Botany L V(JL - 8 



Setchell and Gardner, Phyc. Cont, VII, 1924, p. 12. Cylindro- 

 carpus rugosa Okamura, Alg. Japon. Exsicc, no. 88, 1903, Icon, Jap. 

 Alg., vol. 1, 1907, p. 20, pi. 5, figs. 1-6. Petrospongiuni Berkeleyi 

 Collins, Holdcn and Setchell, Phyc. Bor.-Amer. (Exsicc), no. 232, 

 IS!) 6 (not of Naegeli). 



This enrions, dark colored, rather firm, yet carnose plant is com- 

 mon on rocks exposed to snrf along the central Californian coast and 

 has been found on that of southern California as well. Its peripheral 

 filaments differ in size (about twice the diameter) and in branching 

 from those of the European species and agree closely with those of the 

 Japanese species. 



16. Leathesia Gray 



Fronds irregularly globose, solid in the juvenile stage, soon becom- 

 ing hollow in some species and remaining solid in others, decidedly 

 carnose, interior consisting of radiating, dichotomously or trichotom- 

 ously branched filaments composed of large, irregular, colorless cells 

 toward the base or center as the case may be, merging into smaller 

 cells toward the periphery ; cortex composed of a short series of small, 

 color bearing cells set in a firm mucous matrix; zoosporangia and 

 uniseriate gametangia known, both arising at the base of the cortical 

 filaments; hairs single or in fascicles. 



Gray, Nat. Ar. Brit. PI., vol. 1, 1821, p. 301. 



The genus Leathesia, as understood and interpreted by us, should 

 include the Corynophlaea and Corynephora of Kuetzing (1843, p. 331). 

 The chief distinction between Corynophlaea and Leathesia as diag- 

 nosed, seems to be that in Corynophlaea the adult thallus is attached 

 by a single layer of cells from which arise all the other cells, forming 

 a flattened, hemispherical or spherical, solid structure depending upon 

 the nature of the substratum, while in Leathesia the adult thallus is 

 more or less spherical and usually hollow. Structurally and in mode 

 of development there seems to be no fundamental difference. The 

 basal part is practically the same in both genera in the early stages 

 of development (cf. Oltmanns, 1922, p. 26, but cf. also Okamura, 1907, 

 p. 81, pi. 18, figs. 9-14). The cells of the basal portion are more or 

 less modified to serve as attaching cells in both genera, It is difficult 

 to determine in the diminutive species of both genera whether or not 

 all of the specimens are solid or hollow. Kuetzing indeed transferred 

 the type species of his genus Corynophlaea, C. oaltica, to his genus 

 Corynephora in Tabulae Phycologicae (1858, pi. II), which is hollow 



