2l6 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3D Ser. 



Porfhyra when found floating are in a very poor condition 

 it seems very unlikely. One would rather be inclined to 

 ascribe the greater development of specimens of P. amplis- 

 sima to little exposure, since, judging from notes appended 

 to specimens examined, it appears to be due to the plants 

 growing in undisturbed water, while specimens collected in 

 exposed places always were small. 



The shape of the fronds is to a certain extent variable. 

 The extreme forms are broadly elliptical and ovate-lanceo- 

 late. Between these two a large number of intermediate 

 forms may be noted. The diversity in form is perhaps due 

 to a great extent to mechanical influences. An important 

 factor is also the age of the specimen. The older, longer 

 plants seem to possess a greater lateral development, out of 

 proportion to the increase in length. 



The color seems hkewise to depend on the age of the 

 plant. The younger specimens vary from lake to deep red- 

 purple, but the color seems to fade out in the older speci- 

 mens, which are often a faint brownish red. 



The fronds are densely folded, the folds extending to the 

 median line of the frond. The margin is smooth or lacini- 

 ate, a matter which also probably depends on greater or 

 less exposure. 



The base is as a rule more or less cuneate. In some 

 specimens the base is strongly cordate. Many intermediate 

 forms may be met with. Our plants from Alaska are not 

 stipitate and in this regard differ from Kjeflman's descrip- 

 tion. They are sessile upon a small disc, much smaller than 

 the one we find in Porphyra perforata. 



The thickness of the frond varies from fifty to eighty 

 microns. The majority of the specimens, however, meas- 

 ured about sixty microns, both in the vegetative and in the 

 reproductive parts. The shape of the cells in the middle 

 of the frond is, in cross-section, square or slightly higher 

 than broad. 



The plant is as a rule monoecious, sporocarps and anther- 

 idia occurring side by side, as shown in figs. I3« and I3(5. 

 Frequently one cell develops into antheridia, while the 



