278 



STRUCTURAL BOTANY 



TYPE XXV. CLADOTHEIX DICHOTOMA. 



We have chosen this plant as an example of another 

 group of Bacteria, which probably, however, are rather 



remote from the true endosporous 

 Bacilli and their allies. Cladothrix 

 dichotoma is a very common organ- 

 ism in impure water. A very 

 moderate degree of impurity is 

 sufficient to provide it with food, 

 for it sometimes appears in vast 

 quantities in the pipes of an ordinary 

 water-supply, where it forms dirty- 

 white masses, which may even choke 

 up the taps. 



In its vegetative condition the 

 plant forms long branched threads, 

 attached at one end to some solid 

 substance. The filaments are com- 

 posed of a single series of rod-shaped 

 cells (Fig. Ill), and are enclosed in 

 a gelatinous sheath. The branching 

 is not genuine, for it does not depend 

 on the formation of lateral out- 

 growths, or on a true dichotomy of 

 the growing-point. The gelatinous 

 sheath offers a certain resistance to 

 the growth of the filament within, 

 which consequently breaks across, 

 and the two parts grow past each 

 other at the point of rupture. Exactly the same kind of 

 apparent branching occurs in some of the blue-green Algee, 

 which Cladothrix and its allies closely resemble. The 



FIG. 111. A, Clado- 

 thrix dichotoma. 

 Branched vegetative 

 filament. Magnified 

 about 450. B, Creno- 

 thrix. Formation of 

 microspores in a 

 filament. Magnified 

 about 700. C, escape 

 of the microspores. 

 Magnified about 700. 

 ( After Zopf.) 



