LESSONS IN BOTANY. 201 



each other. Write out an account of everything observed, with 

 a description of the locality in which the plant was found. 



In the plants heretofore studied there was little differentiation 

 of parts, but in the marchantia the upper surface seems to have 

 been specialized for the purpose of assimilation and reproduc- 

 tion, and the under side for the absorption of nourishing liquids. 

 And there is some thickening of cell walls, and some indications 

 of the development of a vascular system. Marchantia grows 

 well in greenhouses and may be grown for observation on moist 

 earth anywhere about the house. 



The true Mosses are common wherever moisture is abundant, 

 in swamps, on the ground, on trees, rocks and decaying vegeta- 

 tion. The stem, roots or root hairs and leaves in form and func- 

 tion are similar to those of the higher plants. The spore formed 

 by the sexual organs produces a branching body called the pro- 

 tonema, from which the moss plant proper grows, producing at 

 length the archegonia and antheridia. Mosses may be grown 

 for observation on moist decaying wood or earth under a glass. 



In studying mosses, notice the following: the stem, its height, 

 shape and color, make a cross section of it and note different 

 tissues as shown by different colors. Note the shape, color and 

 arrangement of the leaves; study the flowering heads, the male 

 with its rosette of green leaves, and the female with the 

 leaves folded into a bud ; compare them in other respects ; note 

 the fruit which is a cylindrical pod or capsule, and the hood fit- 

 ting over the pod, remove the hood and note appearance and 

 contents of the pod. Make full notes of what you observe and 

 describe the locality in which the moss was found. 



In the groups previously studied the sexually formed spore 

 produced a plant like the parent, but in this group it grows into 

 a fruit or sporogonium, which forms asexual spores that pro- 

 duce plants like the original. This process is known as an alter- 

 nation of generations. 



In the economy of nature Mosses, with Lichens and other 

 plants of the lower orders, are precursors of higher plants; they 

 appear first on rocks and sterile places ; sand and dust collecting 



