BoT.— Vol. II.] HUS—PORPHYRA. 221 



It is about fourteen centimeters long and ten centimeters 

 broad. It is the writer's opinion that the specimen in ques- 

 tion belongs to the set distributed in the Phycotheca Gener- 

 alis, Fascl. I, No. 8, and referred to by Foslie (1890) when 

 speaking of a specimen of P. miniata communicated to him 

 by Collins, and collected at Nahant, Massachusetts. 



The shape of the fronds of P. tenuissima seems eminently 

 constant. Most specimens are roundish ovate, and are not 

 lobed in the slightest. The fronds are folded, more so than 

 in P. miniata but less than in P. amflissima. The color is 

 a delicate pink. This character together with the thinness 

 of the fronds affords the means of readily recognizing P. 

 tenuissima from other species of Porj>hy7'a having the 

 mintata-Xy^e. of antheridia. 



The base seems to be cordate, and is attached by a small 

 disc. 



The fronds are distromatic throughout. There is some 

 variation in the thickness of the frond and in the shape and 

 size of the cells. While toward the edges the frond is but 

 little more than twenty to thirty microns thick, and vegeta- 

 tive cells, where they occur, are from three to four times as 

 broad as high, the cells being fifteen to twenty microns high 

 and from four to six microns broad, in the lower part of the 

 frond, near the base, the thickness varies from sixty-five to 

 seventy-five microns, and the cells are sometimes square, 

 sometimes twice as broad as high, being about twenty 

 microns broad and from ten to twenty microns high. In 

 this regard our specimens from the west coast agree fully 

 with the description of Stromfelt. 



But it is different with the monoecious character. Strom- 

 felt describes this species as dioecious, only having found 

 sporocarps. But what we know of the variability of the 

 different species of Por-phyra in this respect does not warrant 

 us in referring these specimens other than to P. tenuissima, 

 awaiting a more extended comparison between our forms 

 and those of northern Europe. 



(4) January 2, 1902. 



