570 University of California Publications in Botany [Vol. 8 



Order 4. CHORDARIALES ord. nov. 



Fronds erect, cylindrical, branched or unbranched, arising from 

 a discoid holdfast or from an expanded and lobed horizontal thallus, 

 with terminal, but subapical, growth, of three sets of tissues, central 

 core of vertical rows of elongated cells (often disappearing leaving 

 the erect filaments hollow), an intermediate layer of cells slightly 

 longer than broad or thick, and an outer layer of longer or shorter 

 assimilating filaments, more or less distinct or combined into a cortical 

 tissue, near, or at, whose bases the zoosporangia are formed ; zoo- 

 sporangia immersed among the assimilating filaments ; colorless hairs 

 generally present ; gametangia and gametophytes unknown, the later 

 presumably microscopic. 



In pursuance of the idea stated elsewhere, that those groups of 

 Melanophyceae closely related in general vegetative structure and par- 

 ticularly with the same method of growth in length in which no member 

 is known to occur with gametangia, are to be suspected of possessing 

 microscopic gametophytes, we have established the order Chordariales 

 with the family Chordariaceae as the typical family, which includes 

 Chordaria, typified in Chordaria flag ellif ormis (Muell.) Ag., as the 

 type genus. The method of growth is that designated as subapical, as 

 distinguivshed from trichothallic (e.g.,Ectocarpales and Desmarestiales) 

 on the one hand and truly apical (e.g., Sphacelariales, Dictyo- 

 siphonales, etc.) on the other. The meristematic cells are situated in 

 short apical filaments similar to the external assimilatory filaments, 

 but are not terminal in those filaments, being situated two or three, or 

 occasionally more, cells below the terminal cell. In other respects the 

 structure approaches that of the ^giraceae and the Myriogloiaceae 

 where, however, the growth is trichothallic and both macroscopic 

 sporophytes and macroscopic gametophytes are knoM^n, From Hetero- 

 chordariaceae, the families of this order differ in lacking, so far as 

 known, a macroscopic gametophyte. While the family Chordariaceae 

 can be assigned to the order Chordariales, as the type family, yet the 

 close relationship of the genera Coilodesme and Scytothamnus lead 

 us to add a family for the first (Coilodesmaceae) and one for the second 

 (Scytothamnaceae), although we have no members belonging to the 

 latter within our territory. 



Key to the Families 



1. Assimilating filaments distinct 16. Chordariaceae (p. 570) 



1. Assimilating filaments united into a cortical tissue ...17. Coilodesmaceae (p. 577) 



