128 LABORATORY AND FIELD EXERCISES 



b. Rhizophores and roots. The rhizophores are naked, stem- 

 like organs which Lear the roots at the tip, where 

 the rhizophores come in contact with the soil. What 



FIG. 24. Selaginella martensii 



A, branch bearing cones and showing the leaf arrangements ; B, inner face 

 of a megasporophyll, showing the large megasporangium containing a group 

 of four megaspores (tetrad) ; C, two views of megaspores; I), inner face of mi- 

 cro.sporophyll, showing microsporangium ; E, microspores ; F, diagram of a 

 longitudinal section of cone, illustrating position of microsporophylls and megaspo- 

 rophylls and their microsporangia and megasporangia. From Bergen and Davis's 

 " Principles of Botany " 



would be the function of these rhizophores in the 

 natural habitat of Selaginella ? The rhizophore is 

 also an ancient organ which occurred in the early 

 relatives of Selaginella. 



