214 Puget Sound Marine Sta. Pub. Vol. 1, No. 19 



The absence of utricle hairs is one of the characters separating this 

 species from C. adhaerens. Agardh (2) describes the latter species as 

 always tomentose. Oltmanns (11) points out that the growth of trichomas 

 is periodic; but if they occurred in C. dimorphum at some other season 

 than that in which Svedelius and the writer have studied the plant, scars 

 would be left as in C. tomentosum (9) and C. mucronatum (8). Since the 

 scars are not found in our species it is practically certain that the plant is 

 never tomentose. 



The same questions arise in the study of this species that were en- 

 countered in the study of C. mucronatum (8) ; viz., whether the reproduc- 

 tion is sexual as commonly described for this genus, or whether the re- 

 productive bodies found are asexual spores ; whether, in case reproduction 

 is sexual, the gametes are alike or unlike. The difficulty arises from 

 the fact that only one kind of gametangium was found, and they all con- 

 tained the same kind of gametes or zoospores so far as could be detected. 

 These gametes (?) are borne in slender ovate gametangia, usually 300/i 

 long and 50/a in diameter. They are lateral branches of the utricle aris- 

 ing about 500/A from its end {Fig. 4) ; there are, however, frequent ex- 

 ceptions to this, specially when there are two or three on the same utricle 

 but originating at different levels. When two gametangia occur on the 

 same utricle of C. mucronatum, they are equally distant from the end as 

 a rule (8), but this is not the case in C. dimorphum. In the latter they 

 appear at considerable distances from each other and sometimes are scat- 

 tered along the utricle without any definite order. 



All of the utricles on a plant do not bear gametangia at the same 

 time. In some spots on the thallus nearly every utricle will have one, 

 while in another area near by there will be none. Gametangia are more 

 abundant in centrally located areas than on the margin; but they are oc- 

 casionally found in the latter position, though rarely on the under side 

 of the lobes. Svedelius says that the inner thin-walled utricles bear the 

 gametangia, while the outer thick-walled ones produce branches which 

 are homologous to gametangia. However, the writer has commonly found 

 gametangia on these branches and on the utricles with the thick end wells. 

 Therefore Svedelius' inference of a physiological dimorphism is not 

 justified. 



The young gametangium is first a rounded knob caused by the pro- 

 trusion of the utricle wall. It elongates and becomes densely filled with 

 the protoplasm and chlorophyll that is pushed up into it {Fig. 1). A 

 thick plug develops at the base, and the contents round up into a dark 

 green granular mass {Fig. 4). When mature this mass breaks up into 

 round bright-green gametes {Fig. 10). 



