5 o6 Bower.—Studies in the Phytogeny of the Filiccdes . 
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genesis of the bud, whether it be in relation to the apex of the shoot, or is 
really adventitious. 
We have seen that in Cheiropleuria two strands of the leaf-trace enter 
the petiole : they maintain their identity for some 
distance (Text-fig. 8, i). The following details 
relate to a special case, and may be open to 
variation. About 3 inches above the base of the 
petiole the two strands divide, each into two 
(ii, iii) ; the four resulting strands pursue their 
course thus for about 2-3 inches further (iii), 
when those nearest the median line fuse (iv); 
this takes place about 2-3 inches from the base 
of the lamina. Later they again separate, the 
former arrangement of the four strands being 
resumed (v). The marginal strands then bifurcate 
(vi), to give six strands, the further course of 
which may be followed in the superficial views 
of the base of the lamina. 
A comparison may be drawn with the petiole 
of Dipteris Lobbiana , as regards this behaviour of 
the strands of the petiole. It has been seen that 
the leaf-trace there also originates as two strands, 
which at once divide; so that four strands pass 
up the petiole (Text-fig. 6); thus the condition 
comes to be virtually the same as that seen in 
Text-fig. 8, iii. But at some point about two- 
thirds the distance up the petiole, the pairs of 
strands fuse again, and the two resulting strands 
have an obvious relation to the bifurcation of 
the lamina. 
Such division of strands as this in the petiole 
of Dipteris Lobbiana , and in Cheiropleuria, and 
the subsequent fusion of the strands so as to close 
the gap formed, is only a special case of those 
arrangements commonly occurring in the petioles 
of Ferns, and giving the character of a divided 
leaf-trace. The point is most obvious in those 
cases where the leaf-trace is in other species of 
the genus an undivided strand, as in Dipteris Lobbiana and Plagiogyria 
semicordata (Ann. of Bot., xxiv, p. 431, Text-fig. 2). Such cases as these, 
occurring as they do without any relation to the pinnae or their pinna- 
traces, may be held to be ‘ perforations ’ of the petiolar supply, comparable 
in their nature to the ‘perforations’ so often seen in relatively advanced 
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327 <ES 3 > 
Text-figs. 8 , i-vi. Suc¬ 
cessive transverse sections of the 
petiole of a sterile leaf of Cheiro¬ 
pleuria —i, at the base; ii, about 
3 inches up ; iii, 4 inches; iv, 
6 inches; v, 8 inches; vi, 9 
inches from base. Figs, vii, 
viii, are from a fertile leaf, at 
levels corresponding to Figs, v, 
vi of the sterile leaf, x 8. 
