179 



fertilization ^ Sporogenous filaments are found given off not only from the carpo- 

 gonium but also from other cells in the carpogonial branch; in the latter case, 

 however, fusion between these cells and the carpogonium could not always be dis- 

 cerned, as for instance in fig. 98 E, where two young sporogenous filaments are 

 seen projecting from the carpogonium and the subjacent cell. Older stages are 

 shown in fig. 99 C and E; in C the filaments causing the fusion between the cells 

 of the carpogonial branch are 

 easily visible. The sporogenous 

 filaments are here seen growing 

 out in a horizontal direction from 

 the carpogonial branches. Fig. 



98 /, K show auxiliary cells in 

 contact with sporogenous fila- 

 ments, and fig. 99 G represents 

 probably the same after the fusion. 

 The stages shown in figs. 99 D 

 and 98 L are probably young go- 

 nimoblasts, though sporogenous 

 filaments are not visible. Ripe 

 cystocarps are shown in figs. 99 

 H, I; they consist, as shown by 

 Batters (1. c. pi. XI, fig. 4), of an 

 almost spindle-shaped heap of 

 carpospores which easily segre- 

 gate on preparation. The spores 

 are 14 to 17 f/. in diameter. 



The species has been found 

 in almost all the Danish waters, 

 in depths of 1 to 19 meters. It 

 grows on stones and shells of 

 Mytilus edulis and Littorina littorea, 

 often in company with incrusting 

 Lithothamnia and growing over 

 them. In the North Sea and Ska- 

 gerak it has principally been found 

 growing on the stem of Laminaria 

 hyperborea. The sporangia begin their development as a rule in the autumn; 

 they were found undivided in September and November, ripe in January to July, 

 emptied or abortive in June to September and November. But young sporangia 



' Spermatia have not been found adhering to the trichogynes, and in some cases carpogonia having 

 produced sporogenous fdaments show no interruption of tiie protoplasm over the ventr.il part (fig. 98 E, 



99 £) which might suggest a partlienogenetic development of the cystocarp. 



23* 



Fig. 99. 



Petrocelis lleiinedfu. A, two-celled carpofionial branch, January. 

 B-D, Begtrup Vig, May. B, three-celled carpogonial branch, un- 

 fertilized. C. carpogonial branch after fertilization (?), giving off 

 .s])orogenous filaments. D, young gonimoblast arising from an 

 aiixiliarj' cell (?). E, carpogonial branch giving oft' three sporoge- 

 nous filaments (Skagerak, April). F-G, Hellebaek, .July. h\ carpo- 

 gonial branch giving oft' sporogenous filaments. G, presumed auxi- 

 liary cell fused with a sporogenous filament. H, cystocarp, not 

 fully developed, Lysegrund, May. /, ripe cystocarp, Storebelt, January. 

 300:1. B-0 .390:1. 7 230:1. 



