1922] Gardner: The Genus Fucus on the Pacific Coast 13 



holdfast and the first forking, varying in different species from one 

 centimeter to five centimeters hi length. As the plant grows older the 

 alae wear away, more or less, and the midribs among the segments, or 

 branches, thicken; flat at first, they become more nearly cylindrical 

 and virtually become a part of the stipe. The length of the stipe and 

 its degree of flatness are characters of considerable value in deter- 

 mining species. 



The term segments is understood to apply to those portions of the 

 frond between each forking. Characters of the segments which are of 

 morphological value in determining the species are the general shapes, 

 the most prominent of which are linear and cuneate, thickness and 

 width of the alae, and the extent of the development of the midrib. 

 The nature of the terminal segments is often of pronounced value. 



The growing point is located at the base of a flattened, more or less 

 crescent-shaped pit of considerable depth at the outer ends of the 

 terminal segments. They are thus situated back of what appear to 

 be the ends of the segments. The nature of these terminal depressions 

 is of some diagnostic value. 



Receptacle is a term used to designate the metamorphosed free ends 

 of the terminal segments, for the purpose of developing the reproduc- 

 tive organs, oogonia and antheridia. These organs are borne along 

 with sterile filaments, the paraphyses, in cavities, the conceplacles, 

 scattered in various ways over the surface of the receptacles. The 

 receptacles vary much in shape, even on the same individual, as well 

 as on different individuals and on different species. Some are com- 

 planate and possess little mucilaginous substance, others are much 

 swollen and filled with the same substance and still others are inflated 

 with gases. Receptacular characters, though variable, are of con- 

 siderable value in determining species. 



Cryptostomata, when applied to the genus Fucus, is a term that 

 has been applied to certain cavities scattered promiscuously, or 

 arranged more or less definitely, over the whole frond except the stipe 

 and the holdfast. They are not confined to this genus alone, however, 

 but have been more thoroughly investigated in Fucus than in any of 

 the other genera. They appear in other members of the Fucaceae, and 

 also in several genera of the Laminariaceae. The cavities may or may 

 not have sterile, hyaline hairs, paraphyses, in greater or less profusion 

 and, when present, extruding at times through an opening at the top 

 called the ostiole. These paraphyses disintegrate sooner or later, and 

 even the whole cryptostomata may disappear entirely as the lower parts 



