450 Proceedings of the Royal Irish Academy. 



Giffordia secunda (Kutz.) Batt. 13 iS"". 14 X. 



This species {Ectocarjnis secundus, Kiitz.) Tras found on 

 Alaria esculenta, Desmarestia ligulata, and on Himantlialia 

 lorea. Plants of Giffordia secunda have alternate unilateral 

 branches. 



Bornet made the interesting discovery that the pliirilocular 

 sporangia are not all alike. In one, as we have seen it in 

 Bantrj Bay material, zoospores are large (female ?), and in 

 the other small ("male ?) 



Sauvagean has recently sho'wn that heterogamy (oogamy) 

 obtains in this species — the antherozoids produced in the 

 antheridia fertilise the motile oospheres produced in the pluri- 

 locular sporangia. Those oospheres Tvhich are not fertilised, very 

 often perish instead of germinating parthenogenetically. It 

 TTould also seem that later in the season the oospheres lose their 

 sexuality, and take on the role of zoospores, since it is found the 

 antheridia diminish in numbers, and may disappear altogether 

 at a later season. The bodies vrhich were called antheridia 

 many years ago by Bornet and Thuret are now known to be 

 the true antheridia. The antherozoids contained in the latter 

 are disposed in regular rows, but Bornet and Sauvageau have 

 not been able to demonstrate the nature of the inner structure. 

 The arrangement of the antherozoids suggests that it is 

 chambered, but the walls of the loculi, if they exist, have not 

 been noticed. The antherozoids completely resemble those of 

 Fucus measuring 6-7 ju,. by 1-3 //.. There is a relatively large 

 red spot, and the anterior cilium is several times longer than 

 the body of the antherozoid. 



Sorocarpus, Pringsh. 



S. tivcBformis, Pringsh. HE". 



Boundstone ; with plurilocular sporangia only, in grape-like 

 clusters, visible to the naked eye ; grows on the larger Alg®, 

 forming tufts not unlike those of £. confervoides. 



Isthjnoplea, Kjellm. 



/. spTicerophora, Kjellm. {Ectocarpus sjylKBroplxora^ Pbyc. Brit., 

 pi. 126.) 11 H. 12 T. 4 M. K 14 K 



The unilocular sporangia are globose, sessile, opposite one 

 another, or a ramulus ; epiphytic on Polysiphonia tirceolata, 

 Ptilota elegajis, etc. 



