XIV. ALG^l. 



971 



Fucus vesiculosus. 



Tubercle cut transversely. 



c, conceptacle ; T, cellular thickness 



of the tubercle (mag.). 



Fucus vesiculosui. 

 Section of a <J conceptacle lined with branched hairs bearing the antheridia. 



Fucus vesiculosus. Fertilization. 



A , spore approached by antherozoids ; 



B, spore on which the antherozoids have 



fixed themselves (mag.)- (Thuret.) 



Fucus vesiculosus. 



Fertilized spore, larger, surrounded by a 



mucilaginous membrane, and in which 



appear the first indications of division 



(mag.). (Thuret.) 



Fucus vesiculosus. Section of a 9 conceptacle. 

 o, osteole by which the spores escape. (Thuret.) 



Marine Algce, brown or olive, mucilaginous, very various in form : stemless or 

 caulescent, rounded or elongated, formed into a cup (Himanthalia) , or cord (Chorda], 

 or plate (Laminaria) , or fan (Padina) ; frond with or without nerves, entire or vari- 

 ously cut, sometimes pierced with holes (Agarum), or twisted into a spiral (Thalas- 

 siophyllum) , or furnished with floating bladders (Sargassum, Macrocystis, &c.), or with 

 a fistular stem (EcMonia buccinalis, Nereocystis, &c.). REPRODUCTIVE ORGANS, 

 superficial sporangia under the form of sori ; spores, sometimes proceeding from the 

 condensation of the colouring matter of the fronds (trichosporangia) , very small, 

 furnished with vibrating hairs and endowed with the power of motion, sometimes 

 resulting from a true bisexual fertilization, and then monoecious or dioecious ; the ? 

 (oosporangia) either external or conceptacular, containing 1, 2, 4, 8 large ovoid or 

 globose motionless spores ; antheridia sessile or in branches, oblong or linear ; 



