THE GREEN ALGAE OP NORTH AMERICA 321 



C. MYCOIDEA Karsten, 1891, p. 64, PI. IV, fig. n ; PI. V, 

 fig. i ; Mycoidea parasitica Cunningham, 1879, p. 312, Pis. 

 XUI, XIvIII, at least in part; P. B.-A., No. 763. Frond of 

 several layers, attached to the substratum by rhizoids, with a 

 thin general cuticle ; hairs colored with haematochrome ; very 

 variable in shape and size of cells, amount of hairs, etc. On 

 leaves of various tropical and subtropical trees. Fig. 123. 

 Jamaica . Tropics generally. 



Much confusion has prevailed as to this species, and the name 

 here used ma} 7 not be in strict accordance with the laws of 

 nomenclature ; but it seems safe to use it, as less likely to cause 

 confusion, and it does not involve adding a new binominal to 

 the list, already uncomfortably long. 



Phyllactidium iropicum Mobius, iSSSa, p. 225, PI. VIII, figs. 

 1-15 ; Hansgirgict ftabelligera De Toni, 1889, p. 263, is a doubt- 

 ful form, concerning which there have been somewhat contra- 

 dictory reports by different writers ; it has been reported from 

 Cuba and Porto Rico, and from most tropical countries. It is 

 evidently nearly related to Ccphaleuros ; Karsten, 1891, p. 62, 

 refers it, though with some doubts as to its validity, to the 

 neighboring genus, Phycopeltis. 



Order V. SIPHONOCLADIALES. 



Fronds multicellular, usually more or less branched ; cells 

 multi-, very rarely uninucleate, chromatophore net-shaped, or of 

 numerous small disks. 



KEY TO THE FAMILIES OF SIPHONOCLADIALES. 

 I. Filaments simple, unattached ; sexual reproduction by oospores and 



antheridia. 5. SPHAEROPLEACEAE. 



i. Filaments simple or branched ; sexual reproduction isogamous. 2. 

 2. Main axis distinct, of limited growth. 3. 



2. Main axis usually indistinct ; all axes of unlimited growth. 4. . 

 3. Axis bearing whorls of branches of limited growth and of form dif- 

 ferent from the axis. 4- DASYCLADACEAE. 

 3. Branches either similar to the axis, or forming a terminal tuft or 

 membrane. 3. VALONIACEAE. 

 4. Zoospores and gametes produced in little changed vegetative cells. 



i. CLADOPHORACEAE. 



4. Zoospores produced in distinct, ultimately detached sporangia. 

 Shell boring algae. 2. GOMONTIACEAE. 



Family i. CLADOPHORACEAE. 



Frond of simple or branching, monosiphonous filaments, free 

 or more or less united laterally ; cells multi-, rarely uninucleate, 



