SPHENOPHYLLS 215 



mite; the arrangement, however is different. The 

 cone was a large one four centimetres in diameter 

 and ten or more in Inegth. It bore numerous 

 crowded whorls of compound sporophylls, ten to 

 twelve in each whorl. The sporophyll was divided 

 into six parts, three above and three below, united 

 into one at the base. The three lower segments 

 were sterile, like the bracts of a Calamite, while the 

 three upper were the sporangium-bearing organs, 

 the shield-like fertile scales. The characteristic 

 point is that they here form part of a compound 

 sporophyll, of which the bracts are also part. 



In various species of Sphenophyllum the same 

 arrangement as in Cheirostrobus exists, with im- 

 portant differences of detail. Thus in the cone of 

 Sphenophyllum Romeri each fertile scale bore only 

 two sporangia; this was also the case in S. fertile, 

 but in the latter there were no sterile bracts, both 

 the upper and lower parts of the sporophyll divid- 

 ing up into sporangium-bearing organs. In S. 

 Dawsoni we get the sterile bracts again, but here 

 there was only a single sporangium on each spo- 

 rangiophore (a convenient abbreviation of "spo- 

 rangium-bearing organ"); two of the latter were 

 seated on the upper surface of each bract (fig. 25). 



In all these forms the sporophyll was divided 

 into a lower and upper portion, each being often 

 subdivided. Usually the upper portion consisted 

 of sporangiophores and the lower of sterile bracts; 



