214 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 30 Ser. 



form of P. naiadimi found on Phyllospadix, growing in 

 exposed places, with a smaller, rather orbicular frond and a 

 laciniate margin ; while by P. naiadum f . major, we mean 

 the plant which grows on Zostera, in lagoons and other 

 sheltered places, with a larger, broader frond, and which 

 usually possesses an even margin. 



Only one form of fruit was found, viz. — sporocarps. As 

 in the case of the reproductive bodies of the other species 

 of Porphyra, they are here first formed in the region of 

 the tip, gradually spreading over the whole frond. 



Sporocarps. — In the formation of the sporocarp, the first 

 division is cruciate, followed by a division parallel to the 

 surface of the frond, thus giving rise to eight spores in two 

 tiers of four each (PL XXI, figs. 21a and 21b; PL XXII, 

 fig. 24). At the time of the ripening of the sporocarp the 

 jelly around the spores swells, thus making the frond a few 

 microns thicker, but finally dissolves as does the outer jelly- 

 wall, setting the spores free. 



Dr. Anderson suggests that small molluscs, in rasping for 

 food on eel-grass, cause abrasions, "in which the spores of 

 this Porphyra find a place to adhere;" but careful section- 

 ing has failed to show any injury to the epidermal layer of 

 the eel-grass at the places of attachment of very young 

 fronds. 



Habitat. — The plant has been collected throughout the 

 year. It grows exclusively on PhyUospadix and Zostera. 

 In sheltered places we find it all through the winter, but 

 where the eel-grass is exposed to the direct influence of the 

 tides, the Porphyra disappears about August, to reappear 

 in the prothalloid form about the latter part of January. 



Distribution. — This plant appears to be limited to the 

 Pacific Coast, occurring from Washington to Southern 

 California (48° 10-32° 20' N. lat.). 



Localities. — Puget Sound (de A. Saunders ! ) : Coupeville, 

 Washington (N. L. Gardner!); Ballard Beach, Seattle, 

 Washington (Miss J. E. Tilden!); Crescent City, Del 

 Norte County, California (H. Hus ! ) ; Fort Ross, Sonoma 

 County, California (W. A. Setchell, No. 1789!); Duxbury 



