Download PDF

1925] Setchell-Gardner: Melanophyceae 393
The genus Sphacelaria is composed of species attached in various
ways to the substratum or host, but which lacks any pronounced dimor-
phism such as is to be found in some genera of the Sphacelariaceae.
The erect filaments are always more or less branched and with one
exception show primary vertical partitions of the cells over the greater
extent of their axes and in certain species also show secondary trans-
verse partitions. Hairs may be present or absent and simple or
geminate. Rhizoids may, or may not, be present and may form corti-
cations. Certain species produce propagula of distinctive form while
others may lack them. The sporangia and gametangia are borne on
the axes, never on the rhizoids as in Chartopteris. The gametangia
are plurilocular and all alike or differentiated into oogonia and
antheridia.
Our species are few and not at all abundant or well known. Care-
ful search for additional material is much to be desired. We have
relied particularly upon Sauvageau 's different papers collected under
the general title of Remarques sur les Sphacelariacees (1900-1914) for
guidance in the determination of our west coast forms. We have
arranged the material accessible to us under six species, awaiting
further opportunities for study and verification.
Key to the Species
1. Erect plants showing both primary transverse and longitudinal and regular
secondary transverse partitions 1. S. racemosa (p. 393)
1. Erect plants showing, regularly, only primary transverse and longitudinal
partitions 2
2. Propagula stout with short or no projecting rays 3
2. Propagula slender with elongated rays 4
3. Rays of propagula of 2-3 short cells, attenuated outwards. 2. S. brevicornis (p. 394)
3. Rays of propagula usually of a single cell, broad 3. S. californica (p. 395)
4. Rays of propagula simple 5
4. Rays of propagula bifurcate 6. S. didichotoma (p. 397)
5. Rays of propagula strictly two 5. S. furcigera (p. 396)
5. Rays of propagula in twos and threes in same individual .4. S. subfusca p. 395)
1. Sphacelaria racemosa Grev.
Erect filaments forming tufts 1-7 cm. high, dark brown, irregularly
branched above, arising from a very small, prostrate thallus ; joints
showing several longitudinal and more or less regular secondary
transverse partitions 55-70^ diam. below ; propagula unknown ; zoo-
sporangia 40-50/x long by about 40/x diam. ("60-70/a x 52-60/x."),
borne on short (1 or 2 celled) pedicels irregularly racemosely arranged
on small lateral branchlets; gametangia (not seen in our specimens)
ovate-cylindrical or cylindrical racemosely arranged.