368 
DR JOHN M'LEAN THOMPSON ON THE 
particularly in the small-pinnate species. In J. scalaris the lower surface of the 
pinna may be almost concealed by the revolute margin. Between the veins the 
pinna-margin is delicate and devoid of photosynthetic tissue (text-fig. 7), but around 
Text-fig. 5. 
Text-fig. 6. 
the bundle-endings — which run to the very margin of the pinna — -the mesophyll is 
well developed. The venation is a sympodial dichotomy, the simplest arrangement 
being shown by J. scalaris , the most advanced in J. verticalis. The details of 
Text-fig. 7. 
branching of the sympodium vary considerably in pinnae from the same leaf. The 
most marked variations are in J. verticalis , in which they are mainly accompaniments 
of pinna-size. The fertile pinnae are usually large and have elaborate venation ; the 
small sterile basal pinnae show a much simpler condition (text-fig. 4). 
