Box.— Vol. II.] HUS—PORPHYRA. 197 



The shape of the fronds is far from being constant, and 

 appears, as in other species of Por^hyra, to be strongly 

 influenced by environmental conditions. While the young 

 frond is liable to be more or less linear, even up to the time 

 when it attains a length of from 15 to 20 centimeters, most 

 specimens of that size show a considerable lateral develop- 

 ment. Older specimens are liable to be much laciniate. 



The form of the base, like the shape of the frond, 

 depends on the surroundings; some specimens, probably 

 those which were exposed to the motion of the waves, 

 exhibiting an obtuse base when young, and a more or less 

 cordate base when older. 



The color of the fronds is fairly constant, being as a rule 

 an even gray-purple, which increases in intensity with age. 

 Various shades may be met with. 



The frond is proliferous and deeply folded and at times 

 beautifully crenulate. 



Attachment is by a disc. The aureole around this disc, 

 so pronounced in P. perfo7'ata, is here but slightly marked. 



The vegetative portion of the frond is uniform in thick- 

 ness, measuring from 30-45 microns. The cells are square 

 or from two to three times as high as broad. The angles 

 are always rounded. There is but little jelly between the 

 cells, and the outer layer of jelly is not very thick, though 

 this varies more or less owing to different conditions of 

 exposure to air and heat, measuring about 7 or 8 microns. 



The fronds are strictly monostromatic in the vegetative 

 part. 



Porphyi'a laciniata is as a rule dioecious, though some 

 instances were found when the fronds were monoecious. 

 The fruit occupies a marginal zone. When antheridia and 

 sporocarps are found on the same frond, they occur in 

 patches very much as in P. perforata. The writer has 

 never met an instance where a few sporocarps were inter- 

 mixed with a large number of antheridia, such as are found 

 in the miniata group ; but a larger or smaller number of 

 vegetative cells and monospores may be found among the 

 sporocarps. Nor has he ever found vegetative cells among 

 the antheridia. 



