49 

 Prostrate stem . 



Hot related to creeping stems since they do not root at the nodos, 

 hence no vegetative propagation or migration. Protection the common 

 theory which seems true in Arctic plants. A second theory is that 

 of insxiff icient food supply. A third which seoms more plausihle is 

 that of mechanical necessity. 



6. Rh,j.aome. 



No essential difference between rhizome and creeper except that one 

 is aerial, the other subterranean. 

 Three types of propagation. 



1. Linear type, unbranched. A migrating form. Pu.ncus balticus, 

 example. 



2. Radial type, as clover, forming a mat, center hollow. Fairy 

 ring, often iound in fungus growth*! Most common type and best one. 



3. Circular type. Migration in a circle, found in some orchids. 



7. Bulb and tuber type. Tliis represents the deepest form of stems. 

 Protection one great factor j another, need for storage. This 



type notdpiously conspicuous in desert plants. A reason for such 

 forms is shortness of growing season and great length of unfavorable 

 conditions. Shade conditions also favorable to bulbs. 



8. Rosette type, one kind the permanent rosette; the other, the 



winter rosette. First, xerophytic in habit, desert plants. Need 

 for protection, very important factor in rosette form. In the 

 temporary rosette shows exposure to alternating conditions. Ex. 



Mullein and Oenothera. 



9. Multicipital or Stem — Base — Complex. Reduction of stem to a 



