88 PRELIMINARY STUDIES. 



The Mosses. 



1. Polytrichum commune is decidedly the best Moss to 

 begin with on account of its large size and common occur- 

 rence. It is abundant everywhere by the roadside and in 

 waste places. The plants are from three to eight inches 

 high. The ordinary plant is the gametophyte, i.e., there 

 are male and female plants. The former bear motile 

 cells, which find their way to certain cells borne on the 

 female plants and unite with them. 



In descending the scale of plant life we here first 

 reach plants that have no true roots. A true root has a 

 vascular structure, such as has been seen in the higher 

 plants. The Mosses and other lower plants have rhizoids, 

 which are mere filaments, each either a single cell or com- 

 posed of a series of cells. Examine the rhizoids under the 

 microscope. 



2. Examine a male plant, which may be known by the 

 rose-shaped cluster of leaves at its "top. In the cells of 

 certain modified leaves of this cluster, minute antherozoids 

 are borne. These antherozoids resemble the antherozoids 

 of Ferns, and like them have the power of motion. The 

 antherozoid is the male gamete. 



3. The female plant bears at its very top, concealed 

 among the leaves, an archegonium, i.e.* a cluster of cells 

 containing a cell, the oo sphere, which is capable of receiv- 

 ing antherozoids. The oosphere is the female gamete. 

 The union of the antherozoid with the oosphere pro- 

 duces an oo spore. The oospore is raised up above the 

 top of the female plant by a very slender stalk, the 

 seta, and develops there into the sporophyte form of 

 the plant. This remains fixed here until it has matured 

 its spores. 



4. The enlarged top that develops on the female plant 

 is a sporangium. Examine and draw some of the spores 



