AQUATIC PLANTS USEFUL TO THE MICROSCOPIST. 50 



immediately attract the attention. They are hollow, 

 and usually empty, and have, a spiral thread running 

 around the walls. At certain stages of growth the 

 cell-wall also has one or more small openings, c, so 

 that the water is able to pass in arid fill the cell. 

 This may explain why the plant retains its moisture 

 for so long, and why it is so easily wetted, having 

 become for these reasons, a favorite substance with 

 the florist for packing his bulbs and other small plants 

 when these are to be carried to a distance. 



The second kind of cells, b, is found between the 

 large ones. They are much smaller, narrower, and 

 commonly contain chlorophyl grains, which, while usu" 

 ally not ab.undant enough to tinge the whole moss a 

 bright green, yet give it that beautiful pale hue almost 

 characteristic of it. These cells will probably need to 

 be searched for the first time the beginner studies a 

 sphagnum leaf, as they are not apt to catch the eye, 

 but the difference in structure, especially the absence 

 of the spiral fibre, should serve to distinguish .them 

 from the large, empty cells, which form the chief 

 part of the leaf. 



The moss seems to have no roots. The lowest 

 parts of the thick mass which it makes are usually 

 dark and partly decayed, and it is there that the 

 Rhizopods are most abundantly found, although many 

 sun-loving forms are equally numerous in the brighter, 

 better lighted upper region. On no account should 

 the student pass a sphagnum swamp, nor even a little 

 patch in those places where it grows more rarely, 

 without taking some to be examined at home. Such a 

 gathering will always repay the slight trouble needed 

 to make it. 



