110 Puget Sound Marine Sta. Pub. Vol. 1, No. 12 



frond may fork a centimeter from its base, or it may grow to a length 

 of 10 cm. before dividing. The distance between successive forkings of 

 the branches varies greatly in diflferent plants, but the mature frond has 

 usually divided at least six times. Quite often, instead of forking, the 

 frond gives off smaller branches ; or it may divide into three or more equal 

 j^arts. One frond was found which at the first forking divided into five 

 parts. Three of these were large and branched dichotomously thereafter, 

 and two were small and branched irregularly. This same tendency toward 

 trichotomous or polychotomous branching is noted by Ernst (7) in C. 

 tomentosum. 



The frond and holdfast-cushion consists of continuous, branching, 

 hypha-like threads, referred to as pith-filaments ; and club-shaped branches, 

 referred to as utricles, which extend perpendicularly to the surface and 

 constitute a compact cortex (Fig. 18). According to Berthold (2) the 

 germinating spore of C. tomentosum first produces a branching "rhizom'" 

 from which grows a tuft of erect filaments of equal length. By the 

 "rhizom" he probably refers to the original horizontal filament of the 

 holdfast-cushion, and the tuft of erect filaments is evidently the begin- 

 ning of a frond. Oltmanns (14) describes the germination a little dif- 

 ferently: "Aus der Zygote resultiert ein vertikaler Spross, der 



mit lappiger Scheibe auf dem Substrat festsitzt. An der Basis desselben 



brechen seitwarts diinne Faden hervor. um recht bald 



Blasen zu bilden, die ihrerseits wieder basal aussprossen." Kiister (11) 

 describes in detail the formation of a frond. According to him each utricle 

 is originally the enlarged end of a pith-filament and so at first is growing 

 erect. It gradually turns from the vertical to a horizontal position ex- 

 tending at right angles to its former position. From the base a slender 

 branch which is a new pith-filament grows upward. This finally en- 

 larges at the end and in turn becomes a utricle which bends to a hori- 

 zontal position. Examination of frond tips of C. mucronatum shows this 

 same method of growth to prevail in this species (Figs. 15, 16, 17). 

 That utricles never originate as lateral branches has not been proved. 

 Young branches have been seen a considerable distance from the end 

 of the filament, but whether they are utricles or merely branches of the 

 pith-filament cannot be determined when they are very young (Fig, 20). 



Pith-filaments are 28-40 /x in diameter, thin-walled and usually 

 colorless, though in some cases there is a limited amount of chlorophyll 

 specially in the holdfast-cushion. The filaments at the lower ends are 

 expanded to form a 3- to 4-lobed holdfast, which may be colorless, or filled 

 with chlorophyll (Figs. 3. 4, 5, 8). There is usually a plug, which 

 serves as a cross-wall; just above the holdfast, though the distance be- 

 tween the latter and the first plug varies considerably. The pith-filament 



