THE BLADDER FERXS. 



higher ones. These lowest branches are again 

 divided, each having above and below its mid-stem 

 a row of leaflets. But the upper row of leaflets, 

 near the main rachis, are much shorter than the 

 lower row, and are deeply cleft or serrated. The 

 two leaflets of the lower rows nearest the main 

 rachis are so much developed, that at and near 

 their base they are again divided into lobes, which 

 in their turn are serrated. Curiously enough, 

 however, the disproportion between the size of the 

 leaflets on the upper and lower sides diminishes 

 towards the point of the branch, and the process 

 of division into lobes is also reduced gradually, so 

 that near the tips of the branch the opposite leaflets 

 are equal in size, and being then much smaller 

 than those at the base of the branch, are not again 

 divided into lobes, but are simply jagged or 

 serrated at their edges. Leaving now the lowest 

 pair of branches on the frond, and coming to those 

 immediately above them, we find that this pair, 

 besides being much smaller, has not the same 

 disproportion between the upper and lower leaflets, 

 although those of the upper row are somewhat 

 shorter than those of the lower one. On this 



