554 University of California Puhlications in Botany [Vol. 8 



Order 3. DESMARESTIALES ord. nov. 



Frond erect, filamentous or membranaceous, cylindrical to slightly 

 compressed, ligulate or even broadly membranaceous ; growth terminal, 

 trichothallic ; frond clothed with densely crowded exserted, simple or 

 branched, colored, monosiphonous filaments (hairs) when young or 

 in the growing portion, these filaments early or tardily deciduous as 

 age advances ; tissues several ; reproduction by zoosporangia ; game- 

 tangia unknown, probably borne on a microscopic gametophyte. 



The posse.ssion of longer or shorter, exserted, colored, monosiphon- 

 ous filaments, especially on young plants or younger portions of peren- 

 nial plants, has always been considered as characteristic of Desmarestia 

 and the related genus Arthrodadia. ' It also is characteristic of the 

 later described and very nearly related genus Phaeiirus Skottsb. 

 There have been several other algae with this permanent or partially 

 transient covering of colored monosiphonous filaments, viz. : Mesogloia 

 Andersanii Farlow, Myriocladia Sciurus Harv., M. Chorda J. Ag., 

 M. grandis Howe, M. callitriclia Rosenv., M. Kuromo Yendo, and pos- 

 sibly M. capensis J. Ag. and Mesogloia natalensis Kuetz. The first two 

 seem to have been investigated by Kuckuck, who did not live to publish 

 his results, but some of his notes and sketches Avere used by Oltmanns 

 (1922, pp. 19-22). From these we learn that Kuckuck had assigned 

 Mesogloia Andersonii Farlow (at least in part) and Myriodadia 

 Sciurus Harv. to a new genus " Myriogloea" and had proposed for 

 these a distinct family, presumably named Myriogloiaceae. Reserving 

 the discussion of the different species until later, we may state that it 

 seems best to adopt Myriogloiaeeae, as of Kuckuck and assign it to our 

 newly established order Desmarestiales, since the terminal growth is 

 most typically trichothallic exserted hairs are prominent, mono- 

 siphonous and colored, and the reproduction is typically onty by 

 zoosporangia. 



Key to the Families 



1. Cortical filaments free 14. Myriogloiaceae (p. 555) 



1. Cortical filaments coalescent into a tissue 15. Desmarestiaoeae (p. 558) 



