XI. THE VARIOUS FORMS OF PLANTS AND HOW THEY 

 REPRODUCE THEMSELVES 



Problem XX. Some forms of plant life. (Optional.} (Labo- 

 ratory Manual, Prob. XJC.) 



(a} An alga, 

 (b/i A fungus. 

 (c) A moss. 

 (cF) A fern. 



Simplest Plant Body a Thallus. It has been found by botanists 

 that the plants which are the simplest in body structure are those 

 which live in the water. Sometimes such simple plants are found 

 upon rocks or on the bark of trees. In such plants we can distin- 



, guish no root, stem, or leaf. 



The plant body may even be 

 spherical in outline and con- 

 sist of but a single cell. Such 

 are the plants (pleurococcus) 

 which give the green color to 

 the bark of trees. Still other 

 plants are threadlike in ap- 

 pearance. Others, as sea- 

 weeds, have a ribbon-shaped 

 body. All these diverse shapes 

 of plant body are grouped under the general name of thallus. The 

 simplest forms of plants have a thalluslike body. 



Adaptation to Environment. Plants, as well as animals, are 

 greatly affected by what immediately surrounds them, their environ- 

 ment. We have shown in our experiments that the environment 

 (conditions of temperature, moisture, soil, etc.) is capable of chang- 

 ing or modifying the structure of plants very greatly. The changes 

 which a plant or animal has undergone, that fit it for conditions in 

 which it lives, are called adaptations to environment. 



144 



A red seaweed, an example of a thallus 

 body. 



