1922] Gardner: The Genus Fucus on the Pacific Coast 15 



have the conceptacles promiscuously distributed over practically the 

 entire frond. In others, e.g., Fucus, Pelvetia, the reproductive struc- 

 tures are limited to the metamorphosed ends of the segments. The 

 cryptostomata in the genus Fucus are so intimately associated with 

 the conceptacles, both being the same in their method of origination 

 and similar in their form, as to make it seem quite logical to conclude 

 that they are degenerated conceptables. Indeed Bower has so considered 

 them, speaking of them as "incomplete sexual conceptacles." Adopt- 

 ing this line of reasoning one may readily conceive that it is only a 

 step further in the line of reduction evolution to produce a plant in 

 which none of the cryptostomata develop paraphyses and all remain 

 completely arched over, leaving no ostioles. Fucus on the west coast 

 of the United States abounds in forms having structures of this nature. 

 Such cavities I have designated caecostomata as distinguished from 

 cryptostomata. and I am using them as one of the distinguishing 

 characters of a species major, viz., Fucus furcatus (see above, p. 9). 

 The next stage in reduction would be the complete elimination of both 

 caecostomata and cryptostomata, and approximately this condition 

 exists in the species major, Fucus cdentatus. 



The color character is of considerable value in determining species. 

 This character, however, is subject to a certain amount of variation 

 and cannot be solely relied upon. The color of an individual may vary 

 with age and with exposure. In dense clusters of plants the lower 

 portions have a more intense color than the upper part. All species 

 are darker on drying than in the living state, and the color distinction 

 between species may be more pronounced and constant in the dried 

 specimens than in the living plants. 



The habitat of a plant cannot be said normally to be a specific 

 determinant, though a knowledge of the normal habitat of a plant, if 

 markedly different from that of another plant, may assist in estab- 

 lishing to a certainty the belief in the entities of two closely related 

 forms. Fucus evanescens f. robustus is never to be found growing 

 outside of a narrow belt along high-tide limit. F. membranaceus f. 

 latissimus inhabits exclusively the lower littoral limit. If there were 

 nothing in gross morphology to distinguish these two species, this fact 

 alone would lend plausible support to the belief that the two are 

 distinct entities, each with a separate lineage. 



