BOT.-VOL. II.] HUS—PORPHYRA. 209 



linear with undulate margin, or deeply laciniate, producing 

 a two-forked frond. Sometimes a specimen, and this is true 

 for those of even 50 centimeters long, measures but one 

 centimeter across ; but the larger specimens may be as wide 

 as 10 centimeters. The average width is 5 centimeters, 

 with a length of 50 centimeters. Mr. R. E. Gibbs, how- 

 ever, collected a specimen of this variety at the Presidio 

 which measured 325 centimeters in length, and with a width 

 of 10 centimeters in the broadest part. The plant was 

 growing on a rock buried in the sand of a gently sloping 

 beach, where it was carried back and forth by the waves, 

 which perhaps brought about its extreme development. 

 Something similar is met with in the linear-lanceolate fronds 

 of P. ferforata when growing in lagoons. 



The base is cuneate to cordate, and is but rarely umbili- 

 cate. The plant is attached by a disc, the structure of which 

 is identical with that of the disc of P. perforata. 



The color of the fronds varies considerably. As a rule 

 the fronds are steel-gray to gray- or yellow-brown; some- 

 times they are in part a bright green. In mature fronds the 

 edges, if the frond is antheridial, are yellow and appear 

 much swollen. The latter is caused by the swelHng of the 

 jelly preparatory to breaking down and setting the anther- 

 ozoids free. The sporocarpic frond is usually of a darker 

 color, the edges having a reddish brown appearance. 



The difference between antheridial and sporocarpic 

 fronds is brought out still better on drying, when the anther- 

 idial fronds become distinctly yellow at the edges, and the 

 sporocarpic fronds, in the region of the sporocarps, red- 

 violet. The latter fronds are also less shiny than the 

 antheridial fronds. 



Occasionally forked fronds are met with; and in such 

 cases it is not unusual to find one fork bearing antheridia, 

 while the other is strictly sporocarpic. These subdioecious 

 fronds form a connecting link between the form and the 

 species proper. 



The number of divisions in the sporocarps and antheridia 

 seems to be the same as in P. ferfoi-ata. 



