130 



DR ROBERT KIDSTON ON 'THE 



Remarks. — This extremely delicate species belongs to the " Selago" type, in which 

 the sporangia are borne on little altered or unmodified portions of the stem, as in 

 Sphenophyllum majus Bronn, sp., # and Sphenophyllum charaeforme Jongmans.f 



The sporangia are pyriform, and, though they may have combined in other numbers, 

 those seen here, where their number can be determined, are united in groups of four. 

 The individual sporangia are very small, including the basal stalk-like portion by which 

 they are united to each other ; they are only 1 mm. long, and slightly narrower. The 

 groups are much broken up ; but at the uppermost node, seen in text-fig. 6, which is 



Text-fig. 6. — Sphenophyllum tenuissimum Kidston. Specimen enlarged 4 times. 



enlarged 4 times, two perfect and one imperfect sporangium are seen united to each 

 other, and the point from which the fourth has been removed is also seen. A photograph 

 of this group, enlarged about 3 times, is given on PI. XVI. fig. 5, where the granular 

 appearance of the sporangia represents the roughness of the matrix and is not 

 organic. 



The leaves are long for the size of the stem. None are perfect, but at text-fig. 6, 

 &', a bifurcation of the limb is seen, and the one remaining perfect segment ends in a 

 sharp point. At b" another fragment of a leaf is preserved, which has also dichotomised. 

 Although one cannot speak with certainty, the leaves probably only forked once, and 

 bore the sporangia on their upper surface in the neighbourhood of the stem, as in 



* Kidston, Mem. Muse'e roy. d'hist. nat. de Belgique, vol. iv. p. 221, pi. xiv. figs. 1-4, 4a ; pi. xv. figs. 2, 3, 1911. 

 t AanahiL d. L. It. /taturhist. Ho/museums. Wien, vol. xxvi. p. 449, pi. vi. and four text-figs., 1912. 



