686 University of California Publications in Botany [Vol. 8 



4. Fucns evanescens f. magnificus Gardner 



Fronds foliaceous, 20-30 cm. high, subcoriaceous, dichotomous or 

 in part secund, dark brown below, yellowish above, olive brown on 

 drying; segments comparatively short, linear to cuneate, more or less 

 twisted, 2.5-3.5 cm. wide, midrib slightly evanescent above, crypto- 

 stomata variable, up to 50 per sq. cm., usually conspicuous with tufts 

 of exserted paraphyses when young; receptacles definitely delimited, 

 very tumid, mucilaginous, simple to decompositely furcate, blunt or 

 acute, very variable in width and length, mostly yellow ; conceptacles 

 moderately numerous and very conspicuous. 



Growing in great profusion in the middle and upper littoral 

 regions. Juneau, Alaska, to Puget Sound, Washington. 



Gardner, Genus Fucus, 1922, p. 48, pis. 51, 52. 



So far as our observations extend, this form seems to be the most 

 abundant of all the forms included in the above mentioned region. It 

 varies widely in the shape of the receptacles. Some receptacles are 

 simple, others decompositely furcate, many quite obtuse, others 

 decidedly acute, but all are definitely delimited and swollen almost to 

 the bursting point with mucilaginous substance. The segments are 

 wide and foliaceous, not narrowing at the forkings, and the tendency 

 to the strict habit of growth often makes them quite contorted. 



One of the distinguishing characters is the sparsity of receptacles 

 maturing at any one time. This habit, marked in only a few of our 

 forms, should receive more study in the field. Our opinion is that 

 the fruiting season extends over a much longer period than in most 

 of the other forms. In the summer season, when we have observed 

 them, one may find on the same individual receptacles varying from 

 completely mature, to others just beginning to form, and many more 

 sterile segments. The fronds fork. One branch of the dichotomj- 

 metamorphoses directly into a receptacle and the other continues to 

 grow, and it in turn may fork one or more times without fruiting. 

 This makes the mature receptacle appear to be lateral in origin, 

 whereas in reality it originates just as all others do. This seems to be 

 the condition prevailing in Thuret's F. platycarpus. Plate 16 in the 

 Etudes Phycologiques well illustrates this condition, but illustrates 

 also another condition which does not seem to occur in f. magnificiis, 

 viz., that the suppressed fruiting segments are alternate, whereas in f. 

 magnificus they are secund. We do not know how regularly the con- 

 dition prevails in F. platycarpus, but this condition is too constantly 

 prevalent in f. magnificus to be overlooked as a diagnostic character. 



