THE DEHISCENCE OP ANTHERS BY APICAL PORES 



173 



cal relations of three groups, leaving the detailed treatment 

 of these and the other types until a later time. 



It seems hardly necessary to define here the terms dehis- 

 cence by apical pores, or apically dehiscent anthers. The 

 terms have been used in the same sense as that in which 

 they are regularly used by systematists. It may be proper 

 to remark, that a precise definition offers considerable diffi- 

 culty. Some genera have anthers opening by a single 

 pore, sometimes at the tip of a rostrate prolongation of the 

 anther, which is never increased down the sides by longitu- 

 dinal slits ; but, except for the Melastomataceae, in an 

 equal or greater number of forms the pores are soon con- 

 tinued more or less down the sides in longitudinal slits. 



^ 



Between dehiscence by the most perfected terminal pore or 

 pores and the primitive longitudinal dehiscence there is a 

 complete series of gradations. In this paper I have fol- 

 lowed quite closely the usage of the best systematists in 

 the description of my material. If an anther shows well 

 defined openings at the tip and there is reason for believing 

 that the pollen is shed largely through these pores, it is 

 generally designated in descriptive works and floras as api- 

 cally dehiscent, or described : " anthers dehiscing by apical 

 pores soon continued down the sides in longitudinal slits." 

 Only living material would permit of an absolute deter- 

 mination. A large proportion of the anthers are thinner 

 along the lateral furrows where dehiscence usually occurs 

 in forms in which the anthers do open by lateral slits, 



and in herbarium material they are liable to be broken 

 along this line even when such might not occur normally 

 in the living plant. Sections cut from anthers which have 

 not broken along this line are very apt to break apart at 

 this point* It is far from easy or even quite impossible to 

 determine whether the lateral slit is a natural occurrence 

 or whether it is due to manipulation. These points will 

 be considered for the forms examined in my final paper, 



