146 THE AMERICAN NATURALIST [Vol. XLI 



The third section, Cheiroglossa, represented by the monotypic 

 0. palmahim L. of the American tropics differs from the others of 

 the genus in having, usually, several spikes which are not generally 

 borne in the median plane of the leaf, but are inserted near the 

 margin. Bower (loc. cit., figs. 116-117) has shown that there 

 may occasionally be a single spike which is then borne in the 

 same position as in 0. pendulum. He supposes that O. palmatum 

 has been derived from the form with a single median spike like 

 that of O. pendulum by branching of the spike, which not infre- 

 quently occurs in the latter species as well as in some others. The 

 separation of the originally connected spikes he assumes has been 

 the result of the great expansion of the lamina, which is much 

 broader in 0. palmatum than in any other species. Unfortunately 

 the developmental history of the sporophyll in 0. palmatum is 

 quite unknown. 



The Young Sporophyll. 

 The differentiation of the two parts of the sporophyll takes 



