CLASSES OF PLANTS 301 



11. On what part of the strawberry are the seeds? Is the edible 

 "berry" an enlarged ovary? What is it? Where are the seeds of the 

 raspberry? The currant? What has happened to the ovary in the 

 case of the apple? The cherry and peach? 



12. Of what use are branches and leaves in electric storms (cf. 

 148)? 



322. Classes of Plants. The plants we have been 

 studying are those highest in development the flower- 

 ing plants. These are composed of many parts, and carry 

 out their functions in complicated ways. There are 

 plants that perform these same functions in much simpler 

 fashion; they may have only a single living unit, or cell, 

 for the carrying out of all their functions. Between the 

 simplest plants and so high a plant as the daisy there are 

 all stages, or grades, of development. We therefore 

 divide plants, for the purpose of studying them, into 

 several groups, or classes, putting together all those that 

 have certain parts, or perform certain functions, nearly 

 alike, and then separating this class as sharply as we can 

 from the plants that do things in an essentially different 

 way. The divisions of plants, as we need to consider 

 them, are algae (pronounced at'-je), fungi (pronounced 

 fun'-jl), mosses, ferns, and seed plants. 



323. Algae. The algae (singular, alga; the g is hard) 

 are chiefly water plants, and vary in size from a single, 

 tiny cell to great masses many feet long. They are green, 

 red, brown, etc., but all contain chlorophyll, and are able 

 to make their own food. A common alga is called pro- 

 tococcus; this is found as a green stain on the north side 

 of trees and fences. When the green material is examined 



