•22 h 



FUCACE/E. [Thallogens. 



whence it glides as far as the mouth. The antherozoids wliich completely fill it, with 

 the exception now and then of the two extremities, soon hegin to be violently 

 .ted; and then the sac opens at either one or both ends, gives them a passage, 

 and they disperse in the water. In Halidrys, Pycnophycns, and Cystoseira, the 

 second envelope of the antherid is absent ; the outer sac only is found attached to 

 the jointed hairs, and the antherozoids are expelled directly from it in a mass ; for 

 some time they remain clustered in a bunch, struggling and turning upon one another 

 before dispersing in the liquid. 



" The antherozoids are very minute hyaline bodies, their length not exceeding the 

 200th of a millimetre. Each contains a granule of a greyish colour in Pelvetia, 

 orange red in all the other genera : it seems sometimes to project from the surface ; 

 but this is probably a mere optical delusion. The locomotive organs consist of two 

 very fine threads of unequal length. The form of these bodies and the arrangement 

 of the threads is not exactly the same in all Fucacese. Thus in Fucus, Ozothallia, 

 and Pelvetia, the antherozoids are in the form of a little bottle, whose neck, which is 

 always foremost, bears the shorter thread, while the longer proceeds from the red 

 granule, and is dragged after it while the body is in motion. Halidrys, Pycnophycus, 

 and Cystoseira present an opposite arrangement : the body of the antherozoid appears 

 ovate or spherical in one direction, compressed and sometimes rather convex in 

 another; the two threads are inserted on the red granule, and during locomotion, the 

 body turns upon itself, carrying before it the longer thread which it moves rapidly, 

 while the shorter is motionless. The antherozoids of Himanthalia have the same 

 structure as those of the three last genera, although the antherids have a double 

 covering as in the three first. Finally, it must be observed that the form of these 

 bodies is not very neatly defined ; they are often combined in small irregular masses ; 

 sometimes no .orange point is to be found ; sometimes there are two. The move- 

 ments are in general very active, and last for many hours ; when they begin to slacken, 

 the undulations of the threads become plainly visible. They cease in fresh water, as 

 well as under the action of iodine, acids, &c. If brought into contact with ammonia 

 the antherozoids dissolve, the orange granule alone remaining. 



" The antherids continue to follow each other for a long time, the same conceptacle 

 containing at the same time young, completely formed, and empty ones. Halidrys 

 siliquosa seems to me to be the only exception. It is to be observed that empty 

 sacs are to be found in conceptacles, the mouth of which is still closed. In Fucacepe 

 when the spores and antherids are produced on different plants, those which bear the 

 hitter arc known by the yellowish colour they communicate to the receptacle or part 

 of the frond where the conceptacles are collected. If fronds in this state are long 

 exposed to contact with air, small orange-coloured protuberances are seen to form at 

 the orifice of each mouth ; these protuberances are viscid and entirely composed of 

 antherids. The same effect is produced by spores, w r hich accumulate at the entrance 

 of the conceptacles in little olive-coloured heaps. This phenomenon is very remarkable 

 when one examines the rocks of the coast at low water in winter; especially if the 

 weather is calm and moist : it gives Fucus vesiculosus and serratus, the two commonest 

 species, a most singular appearance. If the fronds of a Fucus covered with orange- 

 coloured protuberances are washed in sea water, the water becomes loaded with such a 

 quantity of antherozoids, that it acquires a very bright orange colom-, and every drop 

 contains hundreds or thousands of these bodies. If the vessel is then placed near a 

 window the water soon becomes clear, and the antherozoids collect on the lightest 

 . or sometimes on the darkest." 



M. Thuret further observes, that although in some respects the antherozoids would 

 appear to have some fecundating property, yet their resemblance to the zoospores of 

 Pheosporous Algffl is such as to raise a doubt concerning their real nature. For 

 further details tie reader is referred to M. Thuret's memoir in the Annates des 

 Science* Adt unites. 



ADDITIONAL GENERA. 



II'. DROQASTRlD.fi, 



Derbesla, S 

 Cladothele, line. 

 Strux i.i. So 



I ' II. ■ I I. 1 in | 



Kalfsla, B 



Elachtatea, Fries. 

 Scytotbamnus, i 



f. i l ll'irr. 



r.i'iiiriiiii. Barv. 

 Cylindrocarpus, 



( 'niiinn. 



Dion otid.«:. 

 Pinnaria, EndX. 

 Stereocladon, Hook. 



/. 1 1 Barv. 

 Adenocystis, Book. /'. 

 Taonia, J. Ag, 

 Litosiphon, Ilarv. 



FUCIDfi. 



Pelvetia, Thuret & Dec 

 Platythalia, ScrncU r. 



CYSTOSEIRID.fi. 



Contarinia, Endl. 

 Pbacelocarpus, Endl. 



