48 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 12 



ZYGOMITUS Bornet & Flahault, 1889 

 Plant penetrating shells, of irregular filaments, branched, the branch 

 tips commonly attaching to other filaments, uniseriate, the cells shorter or 

 longer than broad, often with oblique end walls, the filaments commonlj'^ 

 forming parenchymatous masses by irregular periclinal and transverse 

 divisions. 



Zygomitus reticulatus Bornet & Flahault 

 Bornet & Flahault 1889, p. CLX, pi. 9, figs. 1-4. 

 Ecuador: Archipielago de Colon, in shells with Mastigocoleus, 

 Hyella, and other perforating algae, Tagus Cove, I. Isabela, no. 34-178 

 (det. F.Thivy), 13 Jan. 1934. 



Valoniaceae 



Plants sacklike, parenchymatous or filamentous, with large, coenocytic 

 cells; septation often delayed after the development of the branching 

 portion of the parent cell; when filamentous the branchlets free and 

 divergent or joined to form nets, but when parenchymatous forming 

 rather massive plants; reproduction by bifiagellate zoospores or gametes 

 from little-differentiated cells. 



KEY TO GENERA 



1. Not bushy 2 



1. Bushy, of branching filaments 3 



2. Plants rounded, multicellular, the cells macroscopic Dictyosphaeria 



2. Plants locally foliaceous, netlike, the primary axis deliquescent; 

 consisting of branches of various orders which unite to form the 

 meshes of the net; branches multicellular, uniseriate . Boodlea, f. 



3. Entangled, spongy, the branching in part opposite, the branches 

 adherent by special tenacular cells Boodlea 



3. With the aspect of a Cladophora; growing continuously from the 

 upper parts of the branches, which although with delayed septa- 

 tion become uniseriate, multicellular Cladophoropsis 



DICTYOSPHAERIA Decaisne, 1892 



Plants rounded, sometimes flattened, laterally lobed or growing 

 together, solid or hollow; multicellular, the cells macroscopic, along their 

 adjacent margins attached to each other by special microscopic tenacula; 

 the under side attached to rocks by short rhizoidal cells. 



