96 PRACTICAL BOTANY. 



together, so that it is difficult to tell where the Alga 

 ends and the Lichen begins. 



OSCILLATORIA. 



Organisms belonging to this genus are to be found 

 as dark blue-green, olive-green, or black coverings on 

 damp walls where water is constantly trickling, on wet 

 soil, c. Mount a small quantity in water, and examine 

 under a high power : they will appear as fine cylin- 

 drical, unbranched filaments, with very delicate cell- 

 walls, and cell-contents of various blue, green, and olive 

 tints. Note the septa dividing the whole into disk- 

 shaped cells : also the convex ends, and the constant 

 oscillating movements, from which they derive their 

 name. 



Staining with the usual reagents will disclose no 

 nuclei, though minute granules may be stained. 



GLOEOCAPSA. 



This organism may be found, usually associated with 

 others, in those slimy masses which frequently grow on 

 the inside of the glass in hot-houses. Examine it 

 under the microscope, and note the numerous cells 

 with pinkish cell-contents, and much swollen cell-walls. 

 The cells will usually be associated in groups, which, 

 from the course of the lines of stratification of the 

 cell-walls, may be seen to have had a common origin. 



The slimy masses of Glceocapsa will rarely be found 

 to consist of it alone ; other organisms being almost 

 always mixed with it. 



