SPENCERITES 191 



wall, and not at right angles to it as in the former 

 genus. 



The winged spores are a remarkable feature 

 of the cone (Fig. 75, A and B). They measure 

 about .14 mm. in maximum diameter (not reckoning 

 the wing), and are thus intermediate in size between 

 the microspores and megaspores of a Lepidostrobus. 

 They are often found still grouped in tetrads, with a 

 tetrahedral arrangement (Fig. 75, B). Around the 

 equator of each spore runs a broad, hollow, annular wing, 

 formed by the dilation of the cuticle (Fig. 75, A and B). 

 It is probable that this wing served the same purpose 

 as the well-known air r sacs of the pollen-grain in Pinus 

 and some other Coniferae, namely to facilitate dispersal 

 by the wind. The form of the air-chamber is, however, 

 quite different, for in Spencerites it constitutes a con- 

 tinuous rim all round the spore (Fig. 75, A), while in 

 the Conifer it forms two distinct sacs, one on each side 

 of the pollen-grain. These spores are thus quite unlike 

 anything known in Lepidostrobus, and at once dis- 

 tinguish Spencerites insignis from allied fructifications. 



Indications of a tissue, or of distinct cells, are 

 frequently found in the cavities of the large spores, 

 but there is reason to suspect that these appearances 

 were caused by the presence of some parasitic organism. 

 No signs of microspores have been detected, and so 

 the homosporous or heterosporous character of the 

 strobilus remains uncertain. 



The anatomy of the axis is of a simple Lycopodi- 

 aceous type, with an axial strand of centripetally 

 developed wood ; in some specimens there is a small 

 pith, which is quite absent in others. The leaf-trace 



