THE LEAF-TRACE IN SOME PINNATE LEAVES. 
19 
Encephalartos Altensteinii, Lehm. 
Encephalartos Altensteinii, Lehm., which has a leaf of the same length as that 
of Dioon spinulosum, has fewer pinnae (about half the number) than that species, 
but its pinnae are twice as broad. The abaxial curve of the leaf-trace in Encephal- 
artos (text-fig. 13) is more of the type of Zamia (text-fig. ll) than of that of Cycas 
or Dioon. On the adaxial face there is a system of additional strands (text-fig. 13a) 
forming a miniature replica-in-reverse of the normal Cycad system (cf the leaf-trace 
shown in text-fig. 12c?, e, with the adaxial portion in text-fig. 13a). Between this 
adaxial system and the abaxial curve there stretches a line of strands across the 
petiole from side to side (text-fig. 136, strands g, f, e, h, k, l, m). It is from the 
tips of this line that the pinna-traces go off. The strands of this line are reinforced 
below the pinnse from the strands on the antero-posterior line * (which are in close 
connection with the strands of the abaxial curve) and from the strands forming the 
adaxial system. The strands of the antero-posterior line give their reinforcement 
to strands e and h (text-fig. 136), while those of the adaxial system join strands 
f and k. Then (to take the supply for one side only) the fusion strands at h and k 
fuse together, and strands l and m fuse with them. From this fusion strand several 
small strands are nipped off in quick succession and pass out together into the pinna 
(text-fig. 13a). The abaxial and adaxial reinforcing systems are gradually drawn 
in towards the pinna-supplying system as one ascends the rachis, until below the 
pair of pinnae sixth from the tip of the leaf the leaf-trace has the outline shown in 
text-fig. 136. Just above the point represented in text-fig. 136, and just below the 
sixth last pair of pinnae, strand c joins strand /and strand c joins strand k. Strands 
d and d' then remain as the representatives of the adaxial system below the fifth 
last pair of pinnae ; strand d joins strand e and strand d' joins strand h prior to the 
formation of the pinna-traces for that pair of pinnae. Above the fifth last pair of 
pinnae, one strand, apparently derived from the strand d', remains to reinforce the 
pinna-supplying system. Above the fourth last pair the adaxial system disappears, 
and to the last three pairs the pinna-traces go off simply from the outwardly-turned 
margins of the series of strands now nearest to the adaxial side of the rachis. 
* And below some of tbe pinnse (the pair twelfth from the tip of the leaf and other pairs below it) from the 
strands at the ends of the abaxial curve. 
