88 STUDIES IN FOSSIL BOTANY 



number of deeply - cut palmate leaves. In some 

 members of the genus, both forms of leaf, the simple 

 and the compound, are .found on the same stem (see 

 Fig- 35); ar »d as, in certain cases, the finely-cut leaves 

 are found below, and the broader wedge-shaped leaves 

 above, a comparison has been suggested with the 

 dimorphic foliage of many aquatic Ranunculi, and 

 other water-plants of the present day. It is a familiar 

 fact that in the Water Crowfoot, for example, the lower 

 submerged leaves are finely divided into capillary 

 segments, while the upper floating leaves are entire or 

 but slightly lobed. Hence it was inferred that Spheno- 

 phyllum itself was an aquatic genus. But this com- 

 parison will not really hold good, for in 5. cuneifolium, 

 for example, the upper cone-bearing branches show the 

 finely-cut foliage, while the leaves of the main stem are 

 often cuneate. 



Apart from this difference in the form of the foliage, 

 there is considerable uniformity in the external 

 characters of Sphenophyllum} The stem was branched, 

 the lateral branches springing from the nodes ; their 

 exact relation to the leaves has not yet been cleared 

 up. The fructification consisted of fairly large cones 

 (Fig- 35)> which from their external appearance might 

 in some cases very well be taken for those of the 

 Calamarieae. We shall see, however, that their organisa- 

 tion was different. 



1 In 6*. speciosum, sometimes separated under the generic name Trizygia, 

 derived from the Gondwana formation (probably Permo-Carboniferous) of 

 India, the six leaves of each whorl are grouped in three pairs, one pair being 

 constantly smaller than the other two. The leaves are accurately super- 

 posed, and the small pair is always on the same side of the stem. A 

 similar differentiation has been observed in some European species of 

 Sphenophyllum. 



