60 

 point, Vewain, also dandelion. A series of stems on one stalk. 

 Ecologically it differs little from rosette stem. Increase of stems 

 but not of plants. 



10. Floating types which vary. 



ll.Thallus — no true stem. Stem and leaf are one and are flat, as 

 Marchantia and duckweed. In Algae the stem and leaf have not "been 

 differentiated, but the duckweed cannot "be so explained. Two 

 theories; one, that water habitat is more favorable for plants 

 hence the plants lose all different parts, the other, that the parts 

 are lost from poverty since the water form is less favoral)le. 

 Latter view seems to be more sensible from experiments which have 

 be'3n' made. 



1. Display of foliage and flowers. 



2. Vegetative reproduction. 

 Vertical stems favor light relations. 

 Horizontal stems favor reproduction. 



3. Protection best favored by the stem working downward. 



4. Mechanical support. 



5. Conduction. The 4th and 5th incidental to the 1st. 



6. Leaf work. 



7. Storage. 



Conflict between 1st, 2d, and 3d causing the different kinds of stem. 

 Moss shows first two types, in the protonema and gametophore. 



