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SYNOPTICAL ARRANGEMENl’
B R I T I S H D I A T O M A C E Æ .
C l a s s CRYPTOGAMIA.
S u b - c l a s s ALGÆ. N a t u r a l O r d e r D I A T O M A C E Æ .
Plant a F r u s t u l e ; consisting of a unilocular or imperfectly septate cell
invested -nitli a bivalve siliceous epidermis. G e m m i p a r o u s in c r e a s e , by
S e e f -D i v i s io n ; during which process the cell secretes a more or less siliceons
C o n n e c t i n g M e m b r a n e . R e p r o d u c t i o n , by C o n j u g a t io n and the
formation of Sporangia.
T r i b e I . Frustules naked; not imbedded
branaceous tubes.
S u b - t r i b e 1 .
nor enclosed in, mempairs,
rarely in greater numbers,
?, or aggregated into a mucous
during self-,
adherent or free,
stratum.
22 G e n e r a . Epithemia, Eunotia, Cymbella, Amphora, Cocconeis,
Coscinodiscus, Eupodiscus, Actinocyclus, Arachnoi-
discus, Triceratium, Cyclotella, Campylodiscus,
Surirella, Tryhlionella, Cymatopleiira, Nitzschia,
Amphiprora, Amphipleura, Navicula, Pinnularia,
Stauroneis, Pleurosigma.
S u b - t r i b e 2 . Connecting membrane subpersistent; frustules after selfdivision
attached by a gelatinous cushion, or dichoto-
mous .
7 G e n e r a . Synedra, Doryphora, Cocconema, Gomphonema, Po-
dosphenia, Rhipidophora, Licmophora.
S u b -t r i b e 3 . Connecting membrane evanescent, or obsolete;
after self-division united into a c o m p r e s s e d filament.
1 2 G e n e r a . Merldion, BacUlaria, ITimantidium, Odontidium, Denticula,
Fragllaria, Eucampia, Achnanthes, Diadesmis,
Rhabdonema, Striatella, Tetracyclus.
S u b - t r i b e 4 . Connecting membrane subpersistent; frustules after selfdivision
united into a zigzag chain.
6 G e n e r a . Diatoma, Grammatophora, Tabellaría, Amphitetras,
Biddulphia, Isthmia.
S u b - t r i b e 5 . Connecting membrane subpersistent as a siliceous annulus;
frustules after self-division united into a cylindrical
filament.
3 G e n e r a . Podosira, Melosira, Orthosira.
T r i b e I I . Frustules invested with a gelatinous or membranaceous envelope.
S u b -t r i b e 6 . Fi-ond indefinite, mammillate; frustules scattered.
1 G e n u s . Mastogloia.
S u b - t r i b e 7 . Frond definite, c o m p r e s s e d or globular; frustules scattered.
2 G e n e r a . Dickieia, Berkeleyia.
S u b - t r i b e 8 . Frond d e f i n i t e , filamentous; frustules in rows.
3 G e n e r a . Encyonema, Colletonema, Schizonema.
S u b - t r i b e 9 . Frond definite, filamentous; frustules fasciculated.
1 G e n u s . Ilonioeocladia.