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PlcelLaph. 1. HYDROPHYTE. 279
Thallus mostly branched ; branches bladdery
Vaucheria. 10.
lliallus entangled, in a determinate form
Iranches clublike Codium. 11,
E. Thalliis jo'mted, jilanientous ; Jilaments flat, Irittle.
Diatomideee.
Joints not banded ; sporidia in transverse
lines Fragilari A. 1 2.
Joints banded transversely, with a cen-
tral spot BiDDULPHIA. 13.
Joints banded longitudinally Diatom a. 14.
F. Thallus jointed, filamentous ; filaments cylindricaly
coupling. Conjugatideae.
Filaments parallel; granules spiral . ^. Conjugata. 15.
Fil. parallel; granules 2-dotted Zygnema. 16.
granules scattered
Fil. bent ;
spores elliptical, in the joint Choaspes. 17.
granules scattered
Fil. bent ;
sporcB cruciform, in the contracted joint . . . Agardia. 18.
Fil., bent ; graiiules scattered ;
sporcB round, in the transverse tubes . . . Serpentina. 19.
G. Thallus cylindrical, anastomosing, netlike. Hydrodictyanide£e.
Filaments anastomosing; spores netlike
Hydrodictyon. 20.
H. Thallus cylindrical, simple, or branched, not couplings
nor anastomosing. Confervideoe.
Thallus from a common base ;
Iratiches pointed, pellucid Myriodactylon. 22.
Thallus fi'om a common base;
branches obtuse, clublike Leathesia. 23^
Thallus from a common axis CniETOPHORA. 21.
Thallus uniform, simple or branched . . Conferva. 25.
Thallus difForm; branches pencilshaped,
jointed DraparnAldia. 24.