Bower . — Studies in the Phytogeny of the Filicales. VI. 23 
gaps, with the much-divided leaf-traces passing obliquely outwards. The 
right-hand trace is complete ; the left-hand has not yet formed its larger 
adaxial strands. In Text-fig. 10, b , these are being separated off ; but 
besides, there is a gap in the lower strap, with several root-strands close by. 
This appears not to be a leaf-gap, but of the nature of a perforation. 
Text-fig. io. a-d. Sections through the rhizome of Leptochilus cuspidatus. a , showing two 
leaf-gaps X, Y, without any perforation ; b, showing the two leaf-gaps, with a perforation (p) ; 
c shows three leaf-gaps, X, Y, z, of which x, Y are lateral and z upon the upper surface; 
d shows the leaf-gap z fully developed, x and Y are almost closed, p, p are perforations of the lower 
meristele. x 4. 
On the other hand, ( c ) shows an arrangement similar to (, a ), but with 
the addition of a gap opening on the upper side, and with already two 
separate strands within it. This is a leaf-gap (z), as a section higher up 
shows ( d ) ; for there it has opened out, and from its margins the complete 
series of leaf-trace strands have been given off. Meanwhile the lateral leaf- 
gaps of the lower leaves (x, y) have almost closed. But there are two other 
