MOSSES AND LIVEEWOETS. 121 



-V. The fructification, — ■ when fully developed a very- 

 conspicuous part of the plant. 



Rhizoids. 



I. Examine the different species with reference to the 

 occurrence of roots. They are found to have the form 

 of hair-like bodies, root-hairs, or rhizoids. Where do they 

 arise ? Are they limited to any one part of the plant ? 



II. Remove some of the rhizoids, mount in the usual 

 way, and examine under the compound microscope. Pre- 

 pare several slides, taking the root-hairs from different 

 species, and from different parts of the same plant for 

 comparison. 



1. Notice first the color, mode of branching, and other 



external features. 



2. Study more closely the minute structure, observing 



the form of the cells composing the rhizoids, the 

 character of their contents, and position of the 

 septa.^ 



3. Notice whether the younger cells of the rhizoids 



differ from the older ones, and if so how. Also 

 whether exposure to different conditions, as a 

 greater or less amount of light, has any effect on 

 the character of the cells or their contents. 



Stem. 



I. Compare the stems of the different mosses, and observe 

 their differences^ of size and habit, contrasting the erect, 

 rigid stem of Climacium with the delicate, spreading 

 branches of Mnium, the minute forms of Barbula with 

 the coarse Polytrichum, and so on. 



1 Cf. Sachs, Physiology of Plants, p. 30. 



