ECTOCARPALES 



153 



sporangia where meiosis has been shown to take place. If they fuse, 

 the zygote develops first into a '' strehlonema'' phase, so-called 

 from the brown alga it resembles, and then into a plantule from 

 which a new adult plant can arise. In this case there is no evidence 

 for the existence of a gametophytic generation, nor has any evidence 

 been obtained to show that such streblonemoid plants can re- 

 produce themselves by means of sporangia. If no fusion of the 

 zooids from the unilocular sporangia takes place the '' strehlonema'' 

 phase is again produced parthenogenetically, but under these 

 circumstances plurilocular sporangia are formed which give rise to 





/ADULTS 



AUTUnN 



^v. 



-^ 



•.Old. bTotonema. 



WINTER 



-^ADULT 

 DioecloLLS 



SPRING- 



/ V 



Ts 



?i 



barlKerio^cnsiLi 



5unnER 

 COLPOMENIA 51NU05A 



Fig. 106. Life cycle of Colpomenia sinuosa. RD = probable place of reduction 

 division in life cycle. (Modified from Kunieda and Suto.) 



a new '' strehlonema'' generation, nor has any investigator under 

 such conditions succeeded in obtaining macroscopic plants 

 again and so it has been suggested, therefore, that sex has been 

 inhibited in these plants. In A. bullosus the zooids from the 

 plurilocular sporangia on the macroscopic thallus do not fuse but 

 germinate directly to give rise to a series of plethysmothalli bearing 

 plurilocular sporangia : these tide over the winter season, and then in 

 spring young Asperococciis plants develop in place of the sporangia 

 on the ectocarpoid plantules. In the unilocular sporangia meiosis 

 takes place and the zooids develop into minute gametophytic 

 plants that produce plurilocular sporangia. If the gametes from 

 these sporangia fuse the zygote develops into a plantule from which 

 a new macroscopic plant arises, but if there is no fusion then they 



