1920] Setchell-Gardncr: Chlorophyccae 179 



Order 3. SIPHONOCLADIALES (blackmax and tansley) 



OLTMANNS 



Thallus iisiially of abundantly branched filaments, or of slightly 

 branched sacks, septate, divisions multinucleate; chroraatophores 

 single and reticulate or numerous and lenticular; sexual reproduction 

 by isoplanogametes. 



Oltmanns, Morph. und Biol, der Algen, vol. 1, 1904, p. 134. 

 SiphonocUdeae Blacknian and Tansley, Class. Green Algae, 1902, 

 p. 119. 



The order Siphonocladiales consists of plants with septate 

 coenocytes, thus differing from the Siphonales which have unseptate 

 coenocytes and from the Ulotrichales whose filaments are made up 

 of cells in the restricted sense. Siphonocladiales are large, richly 

 branched, filamentous species, although a few are unbranched or 

 branched only slightly, while some species are sack-shaped with few 

 and short segments separated from the main portion of the plant. 

 The larger number and more complex families of this order are 

 tropical and marine, but some families are well represented in fresh 

 water also, and in extra-tropical as well as in tropical waters. Almost 

 nothing is known of the tropical forms of our coast. 



The recognition of the group of septate coenocytes among the 

 Chlorophyccae as separate from the group of unseptate coenocytes, is 

 due to Schmitz (1878, 1879, p. 273), who designated it as family 

 Siphonocladiaceae. The placing of this group as a subseries (?) and 

 as being made up of separate families is due to Blackman and Tansley 

 as quoted above, although the content was not exactly coincident with 

 that now generally assigned to the order. Although the idea of a 

 separate group originated with Schmitz, Blackman and Tansley were 

 the first to view it as practically a suborder of Siphonales and as 

 made up of families. 



FAMILY 8. CLADOPHORACEAE (hass.) de-toni (ampl.) 



Fronds of simple or branching monosiphonous filaments, free or 

 more or less united laterally ; septa frequent, enclosing segments with 

 few to many nuclei; chromatophores broad, reticulate or polygonal- 

 lenticular, but arranged in a network and at times connected by 

 slender strands; multiplication by fragmentation and by akinetes; 

 reproduction by 4-ciliated (or possibly 2-ciliated) zoospores and by 

 2-ciliated isogametes, formed in segments slightly, if at all, differ- 

 entiated. 



