SIGILLARIOSTROBUS 233 



Kidston 1 ). M. Zeiller was not able to observe the 

 sporangia in any of his cones (with the exception of 

 a doubtful form to be mentioned immediately). In 

 several specimens, however, he found groups of large 

 spores, obviously megaspores, lying on the upper 

 surface of the sporophylls, as if they had been set free 

 by the breaking down of the sporangial wall. Though 

 the specimens were not petrified, and their internal 

 structure was thus not preserved, it was found possible 

 to isolate and carefully examine the carbonised mega- 

 spores. They are spherical, and of large size, ranging 

 from 1 to 2.25 mm. in diameter in the various species. 

 The cell-wall generally shows three radiating lines, 

 corresponding, no doubt, to the limits of the sister-cells 

 in the same tetrad. ,The membrane may either be 

 smooth or echinulate, according to the species. 



M. Zeiller has also described a small cone, under 

 the name of Sigillariostrobus Crepini? in which the 

 sporangia, but not the spores, can be recognised. In 

 this form, the sporangia appear to be attached at 

 their distal ends to the spoon-shaped laminae of the 

 sporophylls. In dimensions and general organisation 

 this cone agrees very nearly with Spencerites insignis, 

 described in the last chapter. The relation of S. 

 Crepini to Sigillaria is, however, not quite beyond 

 doubt. 



The observations of M. Zeiller established the 

 Cryptogamic nature of Sigillaria, for the fructifications 

 were clearly those of a heterosporous member of the 



1 Kidston, "On the Fossil Flora of the Yorkshire Coal-field," second 

 paper, Trans. Roy. Soc. Edinburgh, vol. xxxix. Part i. 1897. 



2 Zeiller, Bassin houiller de Valenciennes, Flore fossile, p. 605, 

 Plate lxxvii. Fig. 3. 



