ALGAE. FUCA CEAE. 7 1 



serve as a floating apparatus for the thallus which is fixed at its base. In 

 Sargassum short lateral branches swell into bladders and look like stalked berries. 



The Fucaceae have no asexual organs of reproduction, unless \ve reckon as such 

 the adventitious shoots which often appear at the base of the thallus, and according 

 to Reinke are formed endogenously on the filiform branches of the inner cortical 

 cells mentioned above. 



The sexual mode of propagation on the other hand, as we know it from the 

 researches of Thuret and Pringsheim, is highly productive. The antheridia and 

 oogonia are formed in globular cavities (conceptacula\ which appear many 



FIG. 44. FIICHS platycarpus. A end of a larger branch (natural size) ; ff fertile branches. B transverse 

 section of a conceptacle ; d the surrounding epidermal tissue ; a hairs protruding from the orifice ; * inner hairs; 

 c oogonia ; e antheridia. After Thuret. 



together and closely crowded at the end of the longer forked branches or of 

 peculiarly formed lateral shoots. These conceptacles are not formed inside 

 the tissue, but are depressions in its surface which are enclosed by the 

 surrounding tissue and so grown over that at last only a narrow opening remains 

 to the outside 1 . The cellular filaments, which produce the antheridia and oogonia, 



1 According to Bower, On the development of the conceptacle in the Fucaceae (Quart. Journal 

 of Microsc. Sci. 1880), the formation of the conceptacle commences with the dying away and dis- 

 appearance of a cell belonging to the outer cortex ; the growth of this cell was weak from the first. 

 [Valiante (Le Cystoseirae del Golfo di Napoli, Roma 1883) states that in Cystosira the development 

 of the conceptacle takes place by regular cell-division and growth in depressions which arise 

 acropetally at and near the vegetative point.] 



