SPHENOPHYLLEAE. 353 



strand, and has therefore been referred to Sphenophyllum. Bodies like 

 sporangia, but much out of shape, are attached partly in the axils of the 

 leaves, partly to the upper surface of the leaves. Those which originate in 

 the leaves contain granulations of a whitish colour, and it is said that 

 'these can only be microspores ; ' in and close to the axillary bodies 

 are one or more larger bodies which are explained to be macrospores, but 

 which seem from the figure to be pluricellular and to have no very pronounced 

 character. Williamson again has described under the name Volkmannia 

 Dawsoni a fossil, known only in one specimen, which from the structure of 

 its axis may perhaps belong to Sphenophyllum, but which, so far as its 

 imperfect preservation enables us to judge, differs essentially in its other 

 details from the recognised structure of that genus. Of the axis only the 

 outer rind and the central bundle-strand are preserved. The latter does 

 in fact appear to consist entirely of tracheal elements, but they are badly 

 preserved. I satisfied myself of this from some preparations kindly lent 

 me by their owner. The transverse section is three-winged, but the wings 

 are shorter and thicker than is usually the case in Sphenophyllae, and 

 have a broader terminal emargination. The sporangiferous leaves are not 

 bent geniculately upwards, and below they are united into a funnel-shaped 

 continuous plate, from the inner surface of which there arise many stalk-like 

 processes. Several leaves are seen together obliquely cut through on the 

 transverse section, owing to the steepness with which the whorl ascends. 

 Then the space between them is filled with numerous sporangia, which are 

 arranged in a single row between the outer, in several rows between the 

 inner leaves ; and between and close to the latter there are sections to be 

 seen passing irregularly through the before-mentioned stalks, to which 

 Williamson supposes the sporangia to have been attached. I cannot how- 

 ever find clear proof of this in the preparations. The sporangia contain 

 many rather large globular uniform spores with a reticulately ornamented 

 exosporium, which appears on the section to be covered with small prickles. 

 Turning for the last time to the question, to which group of recent 

 plants we shall consider Sphenophyllae to be most nearly related, I find 

 it very difficult to give a positive answer. Different authors have attempted 

 various arrangements, which have been discussed at length by Renault 1 . 

 It has gradually become the custom to bring them into the neighbourhood 

 of Lycopodiaceae. Schenk 2 especially and van Tieghem 3 have very re- 

 cently and earnestly supported this view. Stur 4 and Renault 5 are the only 

 authors who have not assented to it. The former, relying on his theory 

 of the whorl-traces, would class them with Calamariae ; and Renault 6 

 unites them with Salviniae, and has defended this arrangement against 



1 Renault (20). 2 Schenk (10), vol. ii. 3 van Tieghem (3). * Stur (8), (9), and (10). 

 5 Renault (2), vol. ii, p. 81 and (20). 6 Renault (2), vol. ii, p. 81. 



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