1925] Setchell-Gardner: Melanophijeeae 585 



38. Phaeostrophion S. and G. 



Fronds ligulate, solid, polystromatic, more or less stipitate, attached 

 by a small disk ; central tissue composed of elongated cells, irregular 

 in shape and size, merging on each side into smaller parenchymatous 

 cells which in turn merge into palisade-like cortical cells ; reproduction 

 by zoosporangia on both surfaces of the frond immersed in the cortex 

 extending to but not projecting beyond, the surface ; gametangia and 

 hairs unknown. 



Setchell and Gardner, Phyc. Cont., VII, 1924, p. 10. 



The genus Phaeostrophion resembles very closely the genus Enda- 

 rachne in size, general shape and consistency of the frond, but is quite 

 different from that genus in its histological characters and in its 

 method of reproduction. The development of the frond of Phaeostro- 

 phion has not been determined since only old battered specimens are 

 available. The outer ends seem to be the oldest, judging from the 

 more or less battered condition in which the specimens were found. 

 The tissues are almost parenchymatous throughout, but there is a 

 slight tendency in the center of the old fronds to a thick-walled fila- 

 mentous condition, in this respect resembling the central tissue of 

 Endarachne, in which the whole central tissue is composed of narrow 

 intertwined filaments. 



In Endarachne the small surface cells divide tangentially to build 

 up the solid palisade layer of gametangia, but in Phaeostrophion cer- 

 tain cells of the inner layers of the cortex are transformed directly 

 into zoosporangia. In this last character Phaeostrophion resembles 

 very closely the genus Coilodesme which, however, is always hollow. 

 In its parenchymatous character, and in having larger cells in the 

 center and smaller toward and on the surface, it closely approximates 

 to the condition prevailing in the fronds of Ilea Fries. 



The structure of the frond in connection with the method of 

 reproduction would seem to be sufficient to relate Phaeostrophion to 

 the members of the Coilodesmaceae, in which family we propose to 

 place it. 



