458 Proceedings of the Royal Irish Academy. 



Cohort YI. TlLOPTERIDESr^. 



Order. — TiLOPTERiDACEiE. 

 Tilopteris, Kiitz. 



T. Mertensii, Kiitz. {Ectocarpus Mertensii, Ag. Phyc. Brit., pi. 

 cxxxii.) 12 T. + H. + K 



Acinetospora, Born. 



A. pusilla, Born. {Ectocarpus pusillus, Griff. Pliyc. Brit., pi. 

 cliii.) 



Dr. Ed. Bornet has figured the unilocular sporangia, which 

 appear to be extremely rare. (Bull. d. 1. Soc. de Bot. de 

 France, 1892.) 



Cohort YII. — DiCTTOTisr^. 



Order. — Dictyotace^. 

 Dictyota, Lainx. 



LI. Williams ^ has recently shown that the male reproduc- 

 tive bodies of this plant are true antherozoids, each provided 

 with a single spirally-coiled flagellum. These bodies are highly 

 sensitive to light, and active movement is apparently only 

 brought about under the influence of light-stimulus. The 

 oospheres, when liberated, have no cell-wall, attract the an- 

 therozoids, and, if fertilised, begin to germinate at once. If 

 not fertilised, they lose the power of attracting antherozoids, 

 form cell-walls, and, as already described by Thuret and 

 Bornet, germinate parthenogenetically. 



Euckuck,^ when investigating recently the process of repro- 

 duction in 8c%jtosiplion lomentarius, found that fertilisation 

 must occur, if at all, before the oosphere enters the resting 

 condition. 



D. dichotoma,'LQ.m:s.. 10-14. 

 /. implexa, J. Ag. 10-14. 



lAnn. Bot., vol. xi., Dec. 1898. 



^Ber, d. deutsch. Bot. GeseUsch., xvi., pp. 35-37- 



