. Botany of the living plant. Botany. 458 BOTANY OF THE LIVING PLANT Bacteria, The relation of the Bacteria to the Cyanophyceae is obscure. But they certainly offer many points of analogy in their mode of hfe. They are unicellular or filamentous organisms, \Adthout chlorophyll, and they lead a parasitic or saprophytic existence. Their cells may be spherical {Cocais), or rod-shaped [Bacillus), or slightly spiral [Vibrio), or strongly spiral [Spirillum), or straight and slender [Cladothrix), or , grouped in cubical packets [Sarcina). They have a superficial membrane, and protoplasmic body, some-
. Botany of the living plant. Botany. 458 BOTANY OF THE LIVING PLANT Bacteria, The relation of the Bacteria to the Cyanophyceae is obscure. But they certainly offer many points of analogy in their mode of hfe. They are unicellular or filamentous organisms, \Adthout chlorophyll, and they lead a parasitic or saprophytic existence. Their cells may be spherical {Cocais), or rod-shaped [Bacillus), or slightly spiral [Vibrio), or strongly spiral [Spirillum), or straight and slender [Cladothrix), or , grouped in cubical packets [Sarcina). They have a superficial membrane, and protoplasmic body, some- times with chromatin-gran- ules, but no definitely formed nucleus. Many of them are motile, and bear cilia varying in number and position in different types. Their multi- plication is by fission. Their mode of life is best illustrated by an example. The Hay-Bacillus [B. suh- tilis) can be obtained in any decoction of hay, in hot or even in boiling water. If the fluid is filtered and set aside for 48 hours it will be found to be swarming with ciliated Bacilli, while at the surface a scum is formed, which is the " zoogloea " condition of the same plant. In old hay the Bacillus is in the resting condition, as spores, the protoplasm having contracted away from the wall, and being surrounded by a thick membrane (Fig. 391, c). The spores can resist even the temperature of boiling water, and pass still living into the decoction. There they germinate into active Bacilli, motile in the fluid by cilia (Fig. 391, a, d). But those which rise to the surface lose their motility [b), though continuing to divide ; they form thick gelatinous walls, and so they remain associated together as the scum of the zoogloea [e). If the supply of organic material is exhausted they pass again into the resistant spore-stage. It thus appears that a single boiling of the medium containing spores of B. snblilis is not enough to sterilise it, for the spores can resist. Fig. 391. Bacillus subtilis. a,
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectbotany, bookyear1919
