THALLOPHYTA 



FLORIDE^ 



POLYSIPHONIA FASTIGIATA, Grev. 



I. This seaweed is found on all our coasts, growing in dense 

 reddish-brown tufts, which are fixed firmly on to the thallus of 

 Ascophyllum (Ozothallici) nodosum, Le Jolis. It grows to a 

 length of about two inches, and the thin cylindrical thallus is 

 frequently branched in an apparently dichotomous manner : on 

 some of the plants taken in autumn, roundish bodies are borne 

 laterally (cystocarps) ; on others irregular yellowish tassels at 

 the ends of the branches, these are the antheridia, and they 

 are best seen on specimens taken in early summer ; on others 

 again dark irregularly disposed swellings may be recognized in 

 the substance of the thallus, these are the organs of vegetative 

 reproduction (tetraspores). 



II. The material to be used for microscopic investigation 

 should be either quite fresh, and be kept and mounted in salt 

 water, or better in weak glycerine ; or it should be treated while 

 quite fresh with a solution of picric acid in salt water (see p. 5)) 

 and after washing with sea-water, be hardened in successively 

 stronger alcohol from 40 to 90 per cent. 



From material thus treated, select a thallus which does not 

 apparently bear any of the reproductive organs above mentioned ; 

 mount a piece of it, including the tips of some of the branches, 

 in 50 per cent, glycerine and water, and observe under a low 

 power 



