412 A TEXTBOOK OF BOTANY [Ch. X 



Allied to the Flagellates, probably as a specialized off- 

 shoot, is the interesting group of the Peridinece or Dino- 

 flagellata, of which some 150 species exist, mostly free float- 

 ing in the sea. Typical forms are pictured herewith (Fig. 

 281). They are unicellular, possess large brownish-yellow 

 chromatophores, and exhibit remarkable forms, with walls 

 composed often of beautifully sculptured cellulose plates, 

 suggestive of the Desmids and Diatoms later to be con- 

 sidered. Some are luminous when disturbed, and help pro- 

 duce the well-known phosphorescence of the sea. The 

 very highest forms have a simple sexual reproduction. 



Class 4. Myxomycetes : the Slime-molds, or Slime- 

 fungi 

 (Mycetozoa : Fungus-animals) 



These are the slimy, filmy, mold-like masses, of visible, 

 and often considerable, size, which live in damp shaded places, 

 and creep over rotting wood, decaying leaves, humus soil, etc. 

 Later they become converted into spore cases which are 

 often elaborate and beautiful. Over 400 species are known. 



The ordinary plant body, called the Plasmodium, is a mass 

 of protoplasm, much like white of egg in consistency, lacking 

 walls but containing many nuclei. In some species it is 

 compact in form and a few millimeters in diameter ; in others 

 it is a loose open network, as pictured herewith from a 

 typical example (Fig. 282, compare also page 39); in yet 

 others it forms an irregular film or sheet several inches across. 

 The lack of walls and the relatively great size of these Plas- 

 modia render them favorite subjects for investigations upon 

 the characteristics of protoplasm. In color they are typically 

 white or yellowish, but are also pink, violet, and other tints, 

 though they never display the green of chlorophyll. Or- 

 dinarily the Plasmodium lives upon some damp organic 

 substratum upon which it feeds saprophytically, often in- 

 gesting, like an animal, solid pieces of substance from which 

 it later digests the nutritive materials. Commonly it ex- 



