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



jury occurs to some jjart of it. The necessity for cross-partitions of some 

 sort in a plant which grows erect at least in part, and which is composed 

 of filaments many inches in length, is every evident. They keep the cell 

 contents evenly distributed and in their proper place. As evidence of this 

 function it may be said that chloroplasts are often seen piled up against 

 cne side of the plug while there are none on the other side. Plugs sep- 

 arate the contents of gametangia and utricle hairs and prevent an opening 

 into the plant when these organs are broken off. Ernst (7) and Kiister 

 (11) make a point of the fact that two plugs, one on either side of a 

 utricle in the pith-filament, cut it off entirely from the rest of the filament. 

 This is not true in C. mucronatum for there is ordinarily but one plug in 

 the filament near the base of the utricle, and that is just above its origin 

 (Figs. 17, 18, 23). This plug appears while tlie young pith-filamenf grow- 

 ing up from the base of the utricle is still very short. 



The plug is formed by the deposition of successive layers of sub- 

 stance on the inner wall of the filament so that it often appears striated, 

 the lamellae extending in the direction of the filament. An oil immersion 

 lens will sometimes show layers not yet tightly appressed to the pre- 

 ceding ones, leaving spaces between successive layers (Fig. tS). Fig. 49 

 shows the beginning of new layers. There is a striking similarity between 

 the method of formation of the plug and the mucron. Then, too, the sub- 

 stance laid down is apparently the same, judging from the fact that ru- 

 thenium red produced the same reaction in both. Up to the time that 

 plugs are mature a narrow opening is left between compartments of the 

 filament, and by pressing on the cover glass, chloroplasts may be made to 

 pass through it (Fig. 48). The mature plug completely fills the filament 

 for a distance of 30-45 /jl (Fig. 47). 



Characteristic of many plants of C. mucronatum are the utricle haris. 

 — short slender branches, originating near the end of the utricle. Kiister 

 (11) describes them in C. tomentosum as trichome tubes, but the one he pic- 

 tures is different in shape from those of C. mucronatum, being thicker, 

 broader at the base, and approaching more nearly the shape of the gamet- 

 angium of the latter species. Not all plants possess these structures, 

 and even in a plant on which they are fairly common they are not present 

 on every utricle. It has been reported (12) that when C. tomentosum 

 is grown under artificial conditions the utricle hairs branch extensively and 

 sometimes become similar to the utricle in shape. 



The young hairs first appear as rounded projections of the wall of 

 the utricle 180-255 /x from its tip (Fig. 25). In two-thirds of the speci- 

 mens measured this distance was almost exactly 225 fx. As many as six 

 hairs may be found on one utricle but very often there is only one. In the 

 former case they may not be all of the same size, some a few /x's in 



