20 
DR R. C. DAVIE ON 
Bowenia spectabilis, Hook. 
The leaf-trace of Bowenia spectabilis , Hook., has been the subject of a memoir 
by Matte (’05), in which he compares the anatomy of the leaves of a young plant 
growing in the Botanic Garden at Caen. In this account he shows that the usually 
complex leaf-trace in Bowenia is an elaboration of a system with an abaxial curve of 
separate strands and a reinforcing strand on the adaxial face. In his specimens 
( loc . cit., fig. 3) the reinforcing strand is composed of three portions, one going to 
each of the two large pinnae and the third forward to the remaining part of the leaf. 
The appearance of a reinforcing system in this species, which has a bipinnate leaf, 
is a remarkable parallel to the occurrence of a similar system in Encephalartos 
Altensteinii ,* with its long, wide pinnae. There is thus little doubt that the Cycads 
employ the adaxial elaborations of the leaf-trace in relation to heavy pinnae. Matte 
calls attention to the appearance of this adaxial reinforcing .system, and adds 
{loc. cit., p. 415) that it develops in connection with an increasing area of lamina in 
the pinnules or in parts of them. 
The Cycads thus resemble the members of the genus Polypodium among the 
Ferns in developing the abaxial curve of the leaf-trace in relation to the length, of 
the leaf. They differ from them in using the adaxial side of the leaf- trace to develop 
a reinforcing system. 
The reinforcing system in the Cycad leaf- trace is, as in the Fern leaf- trace, 
connected with the presence of large pinnae in the leaf. A resemblance between 
the Cycads and the Ferns appears in the use, common in the Ferns but found only 
in Encephalartos among the Cycads, of the ends of the abaxial curve to form a 
part of the pinna-trace. This (see above, p. 19) occurs in the supply of certain of 
the pinnae in Encephalartos Altensteinii. The amount of vascular tissue which 
passes from the edge of the abaxial curve strands into the pinna-trace is quite small 
in this species, and the method of employing the abaxial curve is confined to a few 
of the pinnae. But the process is interesting, since it occurs in a leaf with large 
pinnae and in a genus which has, as a whole, the largest, if not the longest, pinnae 
among the Cycads. And it is in Fern plants with long leaves and large pinnae that 
the abaxial curve of the leaf-trace is employed directly to provide a part of the 
pinna-trace. In general, then, the Cyeads agree with the Ferns in developing in 
the leaf-trace an abaxial system to carry forward water for a long leaf. From this 
abaxial system the pinnae are supplied indirectly, or (very occasionally in Cycads 
though frequently in Ferns) directly with some of their vascular strands. 
The Cycads, in the genera Encephalartos and Bowenia, where the pinnae are 
large, diverge from the great majority of the Ferns in supplying part of the pinna- 
trace from an accessory adaxial system. 
* Matte (’03, ’04) states that in Encephalartos (but in other species than E. Altensteinii ) 'the adaxial reinforcing 
system is related directly to the pinna-traces in some leaves, 
