268 DR R. KIDSTON AND PROFESSOR D. T. GWYNNE-VAUGHAN ON 
and from the portion of the leaf contained in the block it is evident that it was con- 
tinued below into a round or oval petiole, which bore the curious emergences described 
later on (text fig. 1). 
The leaf is very large compared with the stem that occurs alongside of it, and it 
is possible that it belonged to another and perhaps a larger stem (fig. 1, 1.). In the 
section only about one-half of the total cireumference of the midrib or rachis was 
present, and it contained only four vascular strands. These are of exactly the same 
type as the leaf-traces in the cortex of the stem, but they are on a distinctly larger 
scale. (Compare fig. 25 with figs 20, 21, and 22, which are all of the same magni- 
fication.) The small peripheral elements are more numerous in the strand of the leaf, 
and in longitudinal section there is a greater proportion of scarlariform to porose 
Fic. 1.—Stenomyelon Tuedianum. Free petiole showing vascular strands, ‘‘Sparganum ” cortex, and emergences. x 83. 
(Slide No, 2095.) 
elements. Some of the scalariform elements are almost as wide as the porose, but 
transitional types of pitting are to be observed (fig. 23). The protoxylems are slightly 
immersed, and in one case two were present, indicating an approaching division 
(fiz. 25). In the three strands that were sufficiently well preserved to show the 
protoxylems they were on the side of the xylem nearest the periphery of the midrib 
or rachis. ‘The outer cortex is of the ‘“‘Sparganum” type (figs. 28 and 19). It attains 
a greater development than that seen in the stem,—the sclerotic strands being much 
more numerous and more irregular in form. The dark-coloured resin sacs that occur 
between the fibrous strands in the stem are present in greater number in the midrib, 
and they also occur in its more central parenchyma. The “‘Sparganum” cortex does 
not reach up to the extreme periphery of the petiole, but there is a narrow zone of 
homogeneous parenchyma lying to the outside of it (figs. 31 and 4, par.). At certain 
points this tissue is prolonged into a number of curious emergences (figs. 30, 31, and 
4). They vary greatly in their form and length, some being quite short and blunt 
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