26 



BACTERIA. 



branching spurious ; heterocysts present. Reproduction by syna- 

 kinetes, rarely by resting akinetes and ordinary reproductive 

 akinetes. Tolypothrix, Scytonema, Hassalia, Microchcete. 



Order 7. Sirosiphoniaceae. The individuals are formed of 

 multicellular threads with longitudinal divisions ; true branching 

 and heterocysts, and often distinct differentiation into apex and 

 base. Reproduction by synakinetes, rarely by resting akinetes 

 and ordinary reproductive akinetes. Hapalosiphon, Stigonema, 

 Capsosira, Kostocopsis, Mas/igocolens. 



Family 2. Bacteria.* 



The Bacteria (also known as Schizomycetes, and Fission-Fungi) 

 are the smallest known organisms, and form a parallel group to 

 the Blue-green Algae, but separated from these Algae by the 

 absence of their colouring material ; chlorophyll is only found in 

 a few Bacteria. 



The various forms under which the vegetative condition of the 

 Bacteria appear, are termed as follows : 



1. GLOBULAR FORMS, cocci (Figs. 27, 30 c) : spherical or ellip- 

 soidal, single cells, which, howevei-, are usually loosely massed 

 together and generally termed "Micrococci." 



2. ROD-LIKE FORMS : more or less elongated bodies ; the shorter 

 forms have been styled "Bacterium" (in the narrower sense of the 

 word), and the term "Bacillus " has been applied to longer forms 



which are straight 

 and cylindrical (Figs. 

 28, 29, 30 E). 



3. THREAD -LIKE 

 FORMS : unbranched, 

 long, round filaments, 

 resembling 1 those of 

 Oscillaria, are pos- 

 sessed by Leptothrix 

 (very thin, non-granu- 

 lar filaments ; Fig. 30 

 ^4, the small filaments) 

 and Beggiatoa (thicker 

 filaments, with strong, refractile grains or drops of sulphur (Fig. 



FIG. 23. Spirillum sanguineutn. Four specimens. One 

 has two cilia at the same end, the sulphur grains are seen 

 internally. 



* The Bacteria are more usually included under Fungi. It seems better, how- 

 ever, to place them under the Algae in a separate class with the Suhizophyceae. 



