66 Narrow-Leaved Spleenwort 



have been sown and have produced plants with some normal 

 leaves and with other leaves showing, at a very early stage, 

 similar abnormal lobes. 



In this fern, as in other Asplenii, the sori are borne on veins 

 that stand in certain relations to the midveins, each sorus opening 

 toward a mid vein. Some veins occur that stand in one of the 

 required relations to each of two midveins, and, as a result, two 

 sori (diplazioid sori) sometimes occur on these veins, one sorus 

 opening toward each midvein.* 



Each sorus is borne on a midvein's primary branch, or on 

 this branch's superior basal branch, or on a veinlet of the latter 

 next the midvein. The only veins that stand in one of these 

 relations to each of two midveins, and, consequently, the only 

 veins on which diplazioid sori occur, are the upper basal primary 

 branches of the pinnae's midveins. These branches stand both 

 in the relation of primary branches to the pinnae's midveins and 

 (since the pinnae's midveins are primary branches of the leaf's 

 primary midvein), in the relation of superior basal primary 

 branches of primary branches to the leaf's primary midvein. 

 Diplazioid sori occur only on the upper part of the leaf, perhaps 

 for the reason that the leaf's primary midvein, while showing its 

 character as a midvein in that part of the leaf, apparently loses 

 it below by becoming merged or concealed in the rachis. 



Whether the sori which go to form the diplazioid sori are 

 diplazioid for the whole or only for part of their length depends 

 upon how far they extend. One may extend farther along the 

 upper basal primary branch of the pinna's midvein than the 

 other. At the upper end of this vein, if it divide into two veinlets, 



* For instances of the occurrence of diplazioid sori in other Asplenii, see pp. 72, 



89, and 90. 



