1. Subaerial stems: 

a. These are generally weak or straggling stems growing over the ground and need support for perpetuation. 

b. Sometimes these stems are found to grow beneath the soil surface also. Thus, they show contact with both air and soil. 

c. Subaerial stems are meant for perennation and vegetative propagation. 

d. Scale leaves and axillary buds are present over stem surface. Axillary buds develop into aerial shoots. 

2. Types of subaerial stems: 

a. Trailer: 

1. The shoot spreads over the ground without striking adventitious roots. The branches are either flat i.e. procumbent or partly vertical i.e. decumbent. e. g. Euphorbia, Tridax etc.

b. Runner: 

1. They are special narrow, prostrate or horizontal green branches which develop at the base of erect shoots known as crown. 

2. Runners spread in all directions to produce new crowns with bunch of adventitious roots. 

3. Presence of nodes with scale leaves and axillary buds is observed. 

e.g. Cynodon (Lawn grass) Centella (Hydrocotyl / Brahmi), Oxalis etc. [Any one example] 

c. Stolons:

1. The slender lateral branch arising from the base of main axis is known as stolon. 

2. In some plants it is above ground (wild strawberry). 

3. Primarily stolon shows upward growth in the form of ordinary branch, but when it bends and touches the ground terminal bud grows into new shoot and develops adventitious roots. 

e.g. Wild Strawberry, Jasmine, Mentha, etc.  

d. Sucker: 

1. It is non-green, runner like branch of stem. 

2. It grows horizontally below soil initially and then comes above the soil surface obliquely to produce a new plant. 

3. Sucker can be termed as underground runner. 

e. g. Chrysanthemum, Banana etc.

e. Offset: 

1. These are one intemode long runners in rosette plants at ground or water level. 

2. Offset helps in vegetative propagation. e.g. Water hyacinth or Jal kumbhi (Eichhornia) and Pistia.