1925] getcheU-Gardner: Melanophyceae 697 



19. Fucus evanescens f. ecostatus Gardner 



Fronds submembranaceous, 12-18 em. high, dichotomous or sub- 

 secund, yellowish brown, darker brown on drying, stipe and holdfast 

 fragile; segments strict, cuneate, 5-12 mm. wide, growing point incon- 

 spicuous, midrib very inconspicuous throughout, nearly vanishing in 

 the terminal lobes, alae thin and membranaceous, cryptostomata very 

 few and inconspicuous; receptacles variable, inflated or complanate, 

 mostly narrow, bifid, acuminate ; conceptacles inconspicuous. 



Growing on sandstone, wooden floats, etc., in the upper littoral 

 belt. Coos Bay, Oregon. 



Gardner, Genus Fucus, 1922, p. 39, pi. 39. 



Forma ecostatus is quite abundant at various localities from the 

 mouth of Coos Bay up to its headwaters where several streams of fresh 

 water flow in. This form seems to be definitely fixed, and does not 

 appear to grade into any of the forms that are found growing outside 

 of the bay. More investigation, however, may show T that it is only a 

 depauperate form of some definite species; on the other hand, it may 

 prove to be a distinct species. It varies considerably in size and width 

 of the fronds. The receptacles, though mostly pointed, are at times 

 wide and blunt ; at least there are specimens growing in the same 

 habitat which have the general characters but differ only in the char- 

 acter of the receptacles, and in such cases the segments are generally 

 wider. They are connected, however, by almost imperceptible grada- 

 tions. The size of the plants may be somewhat influenced by the sub- 

 stratum, mostly wood and soft sandstone, neither of which is suited 

 to holding plants for a very great length of time. They usually do not 

 persist in such localities beyond a single fruiting period. If the 

 vanishing of the midrib is to be considered as having any diagnostic 

 value, this form eminently belongs with the evamescens group. The 

 midrib in some specimens is scarcely discernible in any part of the 

 frond, and in all it vanishes in the terminal segments. 



