398 BULLETIN OF THE BUREAU OF FISHERIES. 
very low tides, occurring at the time of the new and full moons, kill every plant growing 
above their level, with the exception of the species noted above, and therefore strictly 
determine the upper limit of all other species in this region. 
The limits of the species growing between tide lines should be noted. Entero- 
morpha, Ulva, Chetomorpha, and Cladophora may be neglected in this connection, since 
these species occur here as mere fragments a few millimeters tall (in some being scarcely 
more than resistant holdfasts) and seem to merely endure the exposure between tide 
lines. Hydrocoleum has been collected only one time, intertwined with Gelidium. 
Lyngbya confervoides forms large mats covering all the walls and many of the jetties 
throughout the harbor from the usual low tide to the usual high-tide line. Fucus has 
about the same vertical range. Gelidium occurs in a zone about 60 cm. wide, from about 
to cm. above the usual low tide to about 12 cm. below the usual high-tide line. Gym- 
nogongrus, with its parasitic Actinococcus, occurs from about ro cm. below to about 
30 cm. above the usual low tides. All of these species are enabled, by their structure, 
to endure prolonged exposure, and all of them except Gymnogongrus seem to require 
emersion, having their lower limits determined by the height of the usual low tides. 
As the great majority of the species occurring here in summer are restricted by the 
heat to the zone below low tides, so those growing here in winter have their upper limit 
determined by the low-tide line on account of the cold, the air temperature sometimes 
falling as low as —9.5° C. No living algze were reported above low water during the 
winter of 1908-9, all plants observed above this line appearing dead. While it is prob- 
able that more careful observation would show the presence of Lyngbya, Fucus, and 
possibly Gelidium and Gymnogongrus between the tide lines, nearly all the species 
undoubtedly have their upper limit determined, as in summer, by the height of the low 
tides. 
In April and May many species occur above low water, but even at this time the 
majority are restricted to the zone below low tides. The vertical distribution of the 
species observed here at this time is as follows: 
OCCURRING ONLY ABOVE LOW TIDE. Champia parvula. 
Lomentaria uncinata. 
Grinnellia americana. 
Chondria dasyphylla. 
Dasya pedicellata. 
Polysiphonia nigrescens. 
Ceramium strictum. 
Lyngbya confervoides. 
Leathesia difformis. 
Porphyra leucosticta. 
Gelidium coerulescens. 
Gelidium crinale. 
OSL SEO E CEIIEN ETON: UAB OCCURRING BOTH ABOVE AND BELOW LOW TIDE. 
Enteromorpha flexuosa. 
Chztomorpha melagonium f. mupincola. 
Cladophora flexuosa. 
Bryopsis plumosa. 
Ectocarpus confervoides. 
Ectocarpus siliculosus. 
Stilophora rhizodes. 
Sargassum filipendula. 
Agardhiella tenera. 
Gracilaria multipartita. 
Enteromorpha linza. 
Enteromorpha prolifera. 
Ulva lactuca. 
Petalonia fascia. 
Fucus vesiculosus. 
Bangia fusco-purpurea. - 
Gymnogongrus griffithsie. 
Hypnea musciformis. 
Chondria tenuissima. 
