310 



BOTANY 



in the swarm -spores of Cladothrix. The ciliary tufts may become 

 so closely intertwined as to present the appearance of a '"single 



thick flagellum. The cilia, 

 although arising from a pro- 

 trusion of the cell protoplasm, 

 are never drawn within the 

 body of the cell, but undergo 

 dissolution before the forma- 

 tion of spores takes place. 

 The existence of such special 

 flagella has not as yet been 

 demonstrated in the Fission- 

 Algae, so that, in this respect, 

 there is a characteristic differ- 

 ence between them and the 

 Fission-Fungi. 



The Fission - Fungi are repre- 

 sented by numerous species, and 

 have a world - wide distribution. 

 Although they present but little 

 variety of external form, the sepa- 

 rate and scarcely distinguishable 

 species exhibit numerous variations 

 in their metabolic and nutritive pro- 

 cesses (of. also pp. 212, 197). A dis- 

 tinction is also made between sapro- 

 phytic and parasitic forms. To the 

 former belong the morphologically 

 most highly -developed species, of 

 which the highest is represented by 

 Cladothrix dichotoma. This Fission- 

 Fungus is found in stagnant water, 

 and consists of falsely branch- 

 ing, delicate filaments (Fig. 229) 

 attached to stones and Algae, and forming a slimy coating over them. The 

 filaments are composed of rod -shaped cells enclosed within an outer filamen- 

 tous sheath. Multiplication occurs through the separation from the parent 

 filament of longer or shorter branches, which pass into a, swarm stage and 

 eventually fall into still smaller rod-like segments. These segments either escape 

 from the enveloping sheath or are set free by its dissolution. Eight or ten flagella 

 spring from a point on the side of the cylindrical swarm segments or, as they are 

 termed, rod-gonidia. After swarming, the rod-gonidia settle down, and attaching 

 themselves to a support grow out into new filaments. 



There are also always found associated with Cladothrix numerous other sapro- 

 phytic Bacteria, Vibriones, Spirilla, Cocci, Zooglcete. It is doubtful whether these 

 are all merely different stages in the development of Cladothrix. This view has 

 certainly not been positively demonstrated as yet by actual continuous observation. 

 Among the most common filamentous Fission-Fungi occurring in water are the 

 Sulphur Bacteria (e.g. Beggiatoa alba), which form smalt granules of sulphur in 



Fig. 229. — Cladothrix dichotoma. 

 filament with rod - shaped 



Part of a branched 

 cells ; treated with 



fuchsin. (After Fischer, x 540.) 



