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REPORT OF THE COMMISSIONER OF FISH AND FISHERIES. 187
Fronds small, tufted, composed of a dense basal portion and an outer portion composed
of free filaments ......................................................................... 28
Fronds tubular, unbranched ........................................................... 29
Fronds filamentous .......................................................................... 31
Fronds membranaceous, expanded ................................................. 41
27. Fronds densely parenchymatous throughout, fruit in external spots Ralfsia.
Fronds minute, thin, formed of a basal horizontal layer of cells and short vertical
filaments, between which the sporangia are borne.
...................................................................................... Myrionema.
28. Free filaments all alike .............................................. Myriactis.*
Free filaments of two kinds, one short and the other exserted.
................................................................................ Elochistea. [sic]
29. Fronds simple, hollow throughout, substance thin .................. 30
Fronds simple, cylindrical, somewhat cartilaginous, with numerous diaphragms
Chorda.
Fronds branching substance thin, sporangia large, arranged in transverse lines
Striaria.
30. Sporangia densely covering the surface .................. Scytosiphon.
Sporangia external in scattered spots ......................... Asperococcus.
31. Fronds capillary, branching, formed of single rows of cells (monosiphonous)
Ectocarpus.
Fronds cylindrical, solid or occasionally becoming partially hollow with age 32
32. Fronds slimy, composed of an axial layer of elongated filaments and a distinct
cortical layer of short, horizontal filaments ............................. 33
Fronds composed of elongated internal cells, which become smaller and polygonal at the
surface ........................................................................................ 35
Fronds, at least in the younger portions, formed of cells of nearly uniform length,
arranged in transverse bands, without any proper cortical layer 38
33. Fronds tough and dense .............................................. Chordaria.
Fronds soft and flaccid ..................................................................... 34
34. Outer cells of cortex producing plurilocular sporangiaCastagnea. Outer cells of cortex
not producing plurilocular sporangia ........................... Mesogloia.
35. Fronds traversed by a central filament formed of large cylindrical cells placed end to
end .............................................................................................. 36
Fronds destitute of distinct axile filament ..................................... 37
36. Sporangia in branching, monosiphonous filaments, which form tufted whorls on the
branches ................................................................... Arthrocladia.
Sporangia inconspicuous, formed from the cortical cells Desmarestia.
37. Sporangia globose, prominent in the cortical layer Dictyosiphon.
*When reference is made in Myriactis and the following genera of Phæosporeæ to free external filaments, it should
be understood that only filaments whose cells contain coloring matter are meant, and that no account is to be taken
of the numerous hyaline hairs with which most of the species of Phæosporeæ are covered at certain seasons.