24 FIRST GROUP. — THALLOPHYTES. 



B. SCHIZOMYCETES. 

 The Schizomycetes ' or Fission-Fungi, known also as Bacteria, are closely 

 connected by their morphological characters with the Cyanophyceae. They 

 are distinguished from them by the entire absence of chlorophyll, which obliges 

 them to feed only on organic substances. Bacteria are organisms which often lie 

 on the very border line of visibility. They consist of short cells, whose diameter 

 is sometimes 5^0 o^ ^ millimetre, but usually considerably less. They are therefore 

 easily confounded with inorganic granules, so that it is often necessary to establish 

 their organic characLer by indirect methods; the most characteristic mark of dis- 

 tinction is their power of dividing and of manifesting active movements very 

 different from the so-called molecular motion of minute particles of inorganic 

 matter. Bacteria occur either isolated or in larger or smaller swarms, and are 

 often united into threads or families. Many forms are motionless at all times, 

 others display a more or less lively and spontaneous motility, due to the presence 

 of cilia, which occur singly at the extremity of the rod-like organism ; in other and 

 filamentous forms the movements correspond to those of the Oscillatorieae. But 

 the motile forms usually pass through stages of their life, in which they are motion- 

 less ; the countless cells that lie close together usually secrete a mass of mucilage or 

 jelly, the shape of which may be sharply defined or be quite irregular ; these gela- 

 tinous colonies, which are often of considerable size, are known as zoogloea-ioxm^. 



The Schizomycetes are the causes of putrefaction proper and of the phenomena 

 of fermentation in the wider sense of the term. They change the sugar of milk, 

 for instance, into lactic acid, so that the milk becomes ' sour,' and the lactic acid 

 by a further process into butyric acid, &c. ; one of them excites ammoniacal fer- 

 mentation in urine. They appear also as the causes of disease in living organisms ; 

 at least there are certain forms of disease, splenic fever for instance, in which the con- 

 nection of these organisms with ihe disease as cause and effect has been established 

 with certainty, while the reference to them of many other infectious diseases is to say 

 the least highly probable. Some species are distinguished by their power of forming 

 pigments. Thus Micrococcus prodigiosiis forms at first on substances containing 

 starch or albumen, as bread, potatoes and paste, small red points which afterwards 

 enlarge into bright red patches. These patches are red masses of mucilage in which 

 countless colourless micrococcus-cells are imbedded. 



The Schizomycetes exhibit great variety of form, as may be gathered from what has 

 been already said. It is to Cohn especially that we are indebted for a discrimination of 

 these forms and their arrangement in genera, and we may recognise among them four 

 main series, the spherical, the rod-like, the filiform, and the spiral. 



' Cohn, Unters. iiber Bakterien (Beitr. zur Biol. d. Pflanzen, Bd. i and 2). — Brefeld, 

 Unters. liber die Schimmelpilze, IV Heft {Bacilhis subtilis). — Nageli, Die niedein Pilze in ihien 

 Beziehungen zu den Infektionskrankheiten, Miinchen, 1877. — Zopf, Ueber den genetischen Zusam- 

 menhang von Spallpilzformen (Monatsber. der Berlinischen Akad. 18S1, p. 277 ff.); [also Die Spalt- 

 pilze, pait of Vol. Ill of Schenk's Handb. d. Botanik.— De Bary, Vergl. Morph. u. Biol. d. Pilze, 

 Mycetozen nnd Bacterien, Leipzig 1884, must be consulted for a succinct account of this group and 

 its copious literature. Of more recent works may be mentioned here Prazmowski, Die Entwick. und 

 Morph. des Bacillus atithracis, Cohn (Krakau 1884, extr. in Bot. Centralbl. XX. 1884). — Fisch, C, 

 Ueber die systemat. Stellung der Bacterien (Biol. Centralbl. V. 1885"). — Baumgarten, Ueber pathog. 

 pflanzliche Mikroorganismen, II. Berlin, 1884. — Grove, Synopsis of the Bacteria and Yeast Fungi, 

 London, 1884— Klein, Micro-organisms in Disease, London, 1885]. 



rmmrr ubrary 



HL C. State College 



