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Rh seen in some normally wind- or insect-fertilized flowers at certain seasons. In fact, we find cleistogamous flowers in our subaqueous plants as well as in their aerial congeners.

Œdogonium ciliatum (?), H., lii.

compressum, H., liii.

1. Bacterium, M. Dic., p. 3.

2. Vibrio rugula (?), M. Dic., p. 3.

3. Spirillum volutans, M. Dic., p. 3.

4. Spirulina jenneri, M. Dic., p. 3.

5. Oscillatoria autumnalis, H., lxxii.

decorticans, H., lxxi.

nigra, H., lxxi.

tenuis, H., lxxii.

limosa, H., lxxi.

contexta (?), H., lxxi.

sp. n. (?)

6. Microleus gracilis, H., lxx.

7. Lyngbya muralis, H., lix.

8. Calothrix.

9. Polypothrix (?).

Oscillatoria.—I have no doubt that with further research this list may be indefinitely extended. The characters of some of the species are not very distinctly marked; and I imagine their nomenclature is not yet settled. Certainly the description and figure of O. autumnalis as given by Hassall are very different from those in the Micrographic Dictionary. The peculiar characteristic of this genus, from which its name is derived, is the singular movements of the filaments. What the cause of these movements is has been the subject of some speculation, but has not been determined. No special organs of motion have been discovered. Whether they are vital or merely mechanical phenomena, is at present impossible to decide. I have seen them in plants which had been immersed many days in Hantzsch's fluid still continuing, feebly but quite perceptibly. The movements are of two kinds—oscillatory and progressive. In the first, the filament, being apparently fixed at one end, sways backwards and forwards upon a centre like the pendulum of a clock, and it may either remain in a state of rigidity, or may curve with a flexibility resembling that of the long thin branch of a tree when agitated by the wind. The other movement is one of direct progression. A filament will, after a period of quiescence, begin to move forward, end on as it were, and having