Fig. 79 Cutleria multifida. A, plant ( x \). B, young plantling. C, 

 plantling slightly older to show branching. D, transverse section 

 of thallus with unilocular sporangia. E, female gametangia. F, male 

 gametangia. G, 'Aglaozonia' stage. (A, original; B-D, G, after 

 Oltmanns; E, F, after Yamanouchi.) 



tufts of hairs, each with a basal growing region, whilst the oogonia 

 and antheridia, which are borne on separate plants, occur in sori on 

 both sides of the thallus. The antheridia are borne normally on 

 threads that are much branched. The mature plurilocular anther- 

 idium contains about 200 antherozoids, each of which possesses 

 two chromatophores, and they are much smaller than the mature 

 ova, each of which contains thirty or more chromatophores. 



The oogonia, with which hairs are sometimes associated, are also 

 formed from superficial cells which divide into a stalk cell and an 

 oogonium initial. The ripe oogonium contains sixteen to fifty-six 

 eggs which, after liberation, remain motile for a period of from 5 

 minutes to 2 hours, whilst the antherozoids can remain active for 

 about 20 hours. Discharge of the gametes takes place at any time 

 during the day but is at its best about 5 a.m., fertilization taking 

 place in the water when the diploid number of chromosomes (48) 

 is restored. No fertilization occurs whilst the ova are motile. Soon 

 after they have become fixed they round off and then they attract 

 large numbers of antherozoids chemotactically. With the passage of 

 time this chemotactic power is lost and has gone completely within 

 3-4 hours. The chances of fertihzation are correspondingly re- 

 duced with the lapse of time from loss of motiUty of the ovimi. If 



143 



