184 CALIFORhUA ACADEMY OF SCIENCES. [Proc. 3D Ser. 



purposes seem to change color on drying. A similar change 

 was noted in sheets of Asakusa Nori (see Economic Uses.) 

 which were of a yellow-brown color when bought in San 

 Francisco, but having been kept for several months in a 

 closed paper box turned purple. A sheet of Asakusa Nori 

 which had accidently been left partially exposed to the air 

 and light for about a month, showed after that time a bril- 

 liant violet coloring in the exposed portion, while that part 

 of the sheet which was not exposed retained its original 

 yellow-brown tint. 



As far as can be judged from the statements of various 

 authors, as well as from our own observations, it appears 

 that the color of certain species varies according to the 

 locality. This is well illustrated by P. leiicosticta Thur. It 

 seems that the European specimens of P. leiicosticta are of 

 a distinctly yellow color when fresh, and when dried a deli- 

 cate purple-pink tint. But the specimens of P. leiicosticta 

 found on the Pacific Coast, if gathered early in the season, 

 are deep-pink, becoming lighter as the season advances. 



From the above, it will be seen that specimens of Porphyra 

 should, whenever possible, be mounted fresh; that even 

 then the color is of small value from a systematic point of 

 view; and that it is most undesirable, in fact, impracticable, 

 to use the color of a frond as the criterion for the species, 

 though it is often of great value in indicating its position. 



It remained for J. G. Agardh to call attention to the 

 monostromatic and distromatic nature of the fronds of the 

 different species of Porphyra. These characters have 

 been found to be absolutely constant in all species, with the 

 exception of those belonging to what we may call the 

 ' ' miniata' ' group, which includes besides P. miniata, P. 

 ampiissima, P. temiissima, and P. abyssicola. The first 

 three species are, as a rule, distromatic, though places may 

 be found which exhibit a monostromatic character, especially 

 towards the edges. Fronds of P. abyssicola, which species 

 was first described by Kjellman as monostromatic, have been 

 found by Rosenvinge and by the author to sometimes exhibit 

 a distromatic character, either through the whole frond or 

 in portions of it. 



