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1925] Setchell-Gardner: Melanophycecu 399
(1922) of his " Morphologic and Biologie der Algen" (p. 2 ct seq.),
has come to the same conclusion. Our present conception of the
Ectocarpales differs from that of Oltmanns in limiting it to families
in which plurilocular gametangia are present on gametophytes slightly,
if at all. different from the sporophyte, or at least definitely macro-
scopic. While the families under Ectocarpales, as limited by us. pre-
sent a very considerable variety in the details of structural differences,
they have in common the possession of plurilocular gametangia giving:
rise to nearly similar gametes (isogamy) and an identity in size and
structure of both gametophyte and sporophyte. The Ectocarpales are
closely related to the Cutleriales, but in the latter there is distinct
oogamy and in some species considerable differences between the two
generations. From the Sphaeelariales, the Ectocarpales differ in the
absence of the conspicuous apical cell of the first mentioned and the
very different cell wall. The cell wall, or the older layers of it, changes
to black in the Sphaeelariales when treated with eau de javelle, but
does not show this reaction in any of the Ectocarpales. The macro-
scopic plants of the members of the Dictyosiphonales, Desmarestiales
and Laminariales are known only with unilocular zoosporangia. The
first and last of these orders are known to have greatly reduced game-
tophytes. From analogy the Desmarestiales may be suspected of being
similar to the other two orders in this respect.
Key to the Families
1. Fronds prostrate, discoid, crustaceous, or pulvinate, never hollow nor carnose,
seldom gelatinous 2
1. Fronds erect, membranaceous or filamentous, when globular or prostrate, either
hollow or carnose 4
2. Fronds wholly discoid, composed of a basal disk of 1 or more layers of
cells giving rise to erect free filaments 3
2. Fronds crustaceous or pulvinate, consisting of a basal cushion of several
layers of cells with penetrating filaments below and erect, free filaments
above 5. Elachisteaceae (p. 502)
3. Fronds small, composed of a disk of 1 or 2 layers of cells all of which give rise
to free, erect filaments or reproductive cells
3. Myrionemataceae (p. 453)
3. Fronds larger (up to several cm. across), composed of a disk of more than 2
layers of cells which give rise to erect, free filaments in sori
4. Ralfsiaceae (p. 493)
4. Fronds globular or flattened, carnose 6. Leathesiaceae (p. 507)
4. Fronds elongated, erect when globular, not carnose 5
5. Fronds membranaceous or flattened, at times hollow 6
5. Fronds cylindrical, not membranaceous 7
6. Sori definite, entirely projecting 8. Asperococcaceae (p. 522)
6. Sori definite, superficial, at times partially projecting
7. Punctariaceae (p. 513)
6. Sori usually indefinite, superficial 10. Scytosiphonaceae (p. 530)