ALGM. 



22' 



air which are forced outwards and serve as swimming bladders. The thallus has not 

 as far as I know, been further minutely examined ; the outer conformation especially 

 has been but little investigated from a morphological point of view. (Gf. Nageli, Neuere 

 Algensysteme.) 



The mode of sexual reproduction is far better known through the labours of Thure 

 and Pringsheim. The antheridia and oogonia are formed in spherical hollows (Con 



Fig. i6o.— Funis platycarpus (after Thuret) ; A end of one of the larger branches (natural size) ; ff fertile branchlets ; 

 B transverse section of a receptacle ; rfthe surrounding epidermal tissue ; a the hairs projecting- from the mouth ; b hairs in 

 the interior; c oogonia, e antheridia (cf. Fig. 2, p. 3). 



ceptacles) which make their appearance in large numbers and densely crowded at th 

 ends of the longer forked branches or of lateral shoots of peculiar form. These re 

 ceptacles are not formed in the interior of the tissue, but as depressions of the sur 

 face which become walled in by the surrounding tissue, and so overgrown that a 

 length only a narrow channel remains, opening outwards. The layer of cells whicl 

 clothes the hollow is thus a continuation of the external epidermal layer of the thallus 

 and since the filaments which produce the antheridia and oogonia sprout from it, thes( 

 latter are, morphologically, trichomes. Some species are monoecious, /. e. both kind 

 of sexual organs are developed in the same receptacle, as in Fucus platycarpus (Fig 

 160); others are dioecious, the receptacles of one plant containing only oogonia, thosi 

 of another plant only antheridia {e. g. Fucus vesiculosus, serratus, and nodosus, Himanthal'u 



this reddish-brown substance phycopheeine. (Compare further the interesting treatise of Rosanofi 

 Observations sur les fonctions et les proprietes des pigments de diverses Algues, in Memoires de 1 

 Soci^t6 des Sci. Nat. de Cherbourg, vol. XIII. 1867 ; and Askenasy, Bot. Zeitg. no. 47, 1869.) [Se 

 also Sorby, Proc. Roy. Soc. 1873, vol. XXI. pp.445' 454' 461-] 



Q 2 



