152 



D. H. Scott. 



Lastly we have in SpJienopJujUnm majns another quite distinct 

 tj^pe of fructification, wliicli is unfortunately only known in the form 



Fig'. 2. Sphenophyllum fertile. A. Diagram of node iu radial section showing- cue 

 sporoph}^!. V. I., ventral lobe; v. s., a ventral sporangiophore, bearing 2 sporangia; 

 V. s.', stnmp of another sporangiophore ; d. I., dorsal lobe ; d. s., a dorsal sporangio- 

 phore; d.s.', stump of another. B. One lobe of sporophyll, seen from above, dividing 

 into 4 sporangiophore« ; in two cases one of the sporangia on each sporangiophore 



is shown. 



of impressions and not in the petrified condition. In this species, as 

 observed by Mr. Kids ton (1902), the bracts of the lax fructifications 



are repeatedly forked, and bear groups of four 

 sporangia, seated near the points of bifur- 

 cation (Fig. 3). In the absence of structural 

 specimens the exact mode of attachment of 

 the sporangia could not be determined, but 

 the species is interesting from the close ana- 

 logies which it appears to present with the 

 fructification of Tmesipteris, as will be further 

 shown below. 



The four types of which the main features 

 liave just been sketched are so distinct that 

 an ultimate subdivision of the genus, based 

 on reproductive characters, appears inevitable. 

 Though further investigations on Spheno- 

 phyllaceous fructifications are much to be 

 desired, it seems evident from our present 

 knowledge that the presence of a dorsiventral 

 lobing of the sporophylls, the ventral lobes 

 constituting the sporangiophores, was cha- 

 racteristics of the group; SpJienophyllum fertile, 

 with both lobes fertile, is probably to be 

 regarded as a special modification rather than 

 as a primitive form. 



Fig. 3. Sphenophyllum ma- 

 jus. Part of forked sporo- 

 phyll in surface vicAV, sho- 

 wing a group of 4 spor- 

 angia inserted below a 

 bifurcation. 

 After Kid s ton. 



