432 CHAKACTP^RS OK THE UKUIER PLANTS less. 



the root is always protected by a root-cap, that of the stem 

 being simply over-arched by leaves. Moreover, an alterna- 

 tion of generations can be traced in all cases. 



Plants may be conveniently divided into the following 

 chief groups or phyla : 



1. A/^([(e. 



2. Fungi. 



3. Musdnece. 



4. Vascu/ar Cryptogams. 



a. Filicinie. 



b. Equisetaceae. 



c. Lycopodinece. 



5. PIiaHeroga7ns. 



a. Gymnosperms. 



b. Angiosperms. 



The Alga are the lower green plants. They may be 

 unicellular, or may take the form of linear, superficial, or 

 solid aggregates : they never exhibit more than a limited 

 amount of cell-differentiation. This group has been repre- 

 sented in the foregoing pages by Zooxanthella, Diatoms, 

 Vaucheria, Caulerpa, Monostroma, Ulva, and Nitella. 



The Fungi are the lower plants devoid of chlorophyll : 

 some are unicellular, others are linear aggregates : in none 

 is there any cell-differentiation worth mentioning. Saccharo- 

 myces, Mucor, Penicillium, and the mushroom belong to 

 this group. 



The position of some of the lower forms which have come 

 under our notice is still doubtful. Bacteria, for instance, 

 are considered by some authors to be Fungi, by others Algse, 

 while others place them in a group apart. Diatoms also are 



