GG6 



PROFESSOR F. O. BOWER ON 



a 



si raightening up and sympodial development of its venation it almost takes the 

 position of a terminal lobe with a midrib. In (/) the pseudo-terminal position 

 appears plainer, though its Venation still appears as a very regular dichotomy. 

 But in (g) the sympodial. development of the veins, both in the pseudo-terminal 

 lobe and in the apparently lateral lobes, has advanced so that each appears to be 



b e 



Fig. 1, a-rj. — Successive juvenile leaves of Osmunda regalis, showing steps of progression from equal dichotomous 

 venation to sympodial branching, and the establishment of a terminal lobe. ( x 5.) 



provided with a midrib in its basal part. At the distal region of each, however, 

 the venation reverts to the original type of almost equal dichotomy. In older leaves 

 the terminal leaflet and lateral pinnae are themselves liable to similar lobing, all 

 having the venation of the type already established in (g). And this architectural 

 method may be continued without further essential modification till the fully 

 formed adult leaf is reached. 



The general characters of these, with their high state of pinnation, are too well 

 known to need redescription. But interest attaches to the origin of the pinnae, their 



