DIV. 



THALLOPHYTA 



407 



flattened segments, and resembles an Opuntia on a small scale. By incrustation 

 with lime it attains a hard, coral -like texture. The segments are formed of 

 branched tubular filaments. 



In Bryopsis the biciliate, pear-shaped, conjugating gametes are differentiated 

 into a larger female cell with a green chromatophore and a smaller male cell, 

 three times smaller than the female and with a single yellow chromatophore ; 



FIG. 347. Tt" - A, Young sporangium. B, Zoospore with the sporangium from 



which it has escaped. C, A portion of the peripheral zone of a zoospore. D, A young plant 

 with rhizoids developed from a zoospore. (A, B after GOTZ ; D after SACHS ; from OLTMANNS' 



Algae. C after STRASBURGER.) 



in J'aucheria and Dichotomosiphon oogamous reproduction is well marked ( 3S ). 

 The latter Algae occur in fresh water or on damp soil. The thallus consists of a 

 single branched filamentous cell attached to the substratum by means of colour- 

 less rhizoids (Fig. 3-47 D). 



The swarm-spores of l\m.cheria t which differ from those of the other Sipho- 

 nales, are developed in special sporangia, cut off from the swollen extremities of 

 lateral branches by means of transverse walls (Fig. 347). The whole contents of 

 such a sporangium become converted into a single green swarm-spore. The wall 



2 D2 



