226 



Siphonales 



Vegetative propagation is known to occur by detached 'leaves' which 

 grow into new plants, and by the formation of rhizome-like branches from 

 the lower part of the thallus. 



Zoogonidia are unknown. 



Numerous biciliated anisogametes are produced in gametangia, which in 

 Bryopsis are converted ' leaves ' but in Pseudobryopsis are ovoid or pear- 



Fig. 146. 1, portion of thallus of Bryopsis cupressoides Lanix. with almost ripe gametangia (#), 

 x about 25. 2, pinnaa of 'leaflet' of Pseudobryopsis myura (J. Ag.) Berth, with gametangia 

 (g) ; 3 and 5 a, copulation of gametes ; 4, zygotes soon after copulation showing chloro- 

 plasts of male (chr") and female (chr') gametes ; 5, zygote in which the chloroplast has 

 divided ; 6, germination of zygote. (From Oltrnanns ; 2 and 3, after Berthold.) 



shaped outgrowths from the ' leaves ' (fig. 146 #). Male and female game- 

 tangia may occur on the same axis or they may be on different plants. 

 The female gametes are about three times the size of the male gametes, 

 possessing a rather large posterior chloroplast with one pyrenoid and a 

 pigment-spot. The male gametes, which are of a brownish-red colour, have 

 only a very small chloroplast and no pigment-spot. The paired cilia are in 



