THE FOSSIL FLORA OF THE YORKSHIRE COAL FIELD. 55 



Sporangium. 



PL II. fig. 12. 



I give here, natural size, a sporangium containing numerous small smooth macro- 

 spores. This sporangium is larger than those of Sigillariostrobus ciliatus, while the 

 macrospores are smaller and smooth, their size being about 0*75 mm. On another small 

 piece of shale from the same locality (No. 1273) there are more or less perfect 

 remains of about a dozen and a half of similar sporangia. 



They may possibly be Sigillarian, but no remains occur along with them to throw 

 any light on their affinities. Two of the macrospores are enlarged ten times at fig. 12a 

 and b. 



These sporangia are evidently similar in nature to those described by Lesquereux 

 under the name of Sporocfstis* 



Affinities of Sigillaria. 



Goldenberg believed that Sigillaria represented an arborescent form of Isoetes,t 

 and though at the time he expressed that opinion, satisfactory evidence in its sup- 

 port was wanting. Subsequent discoveries have, however, proved the accuracy of his 

 suggestion. Two years after he stated these views on the affinities of Sigillaria, he 

 said : — " The great agreement which the Sigillaria bespeak with our quillworts, as 

 well in their internal structure as in their fructification, points to the decision that the 

 Sigillariss were nearly related to the Isoetes, and in the highest probability represented 

 an arborescent form of these plants in bygone times." | 



The Sigillaria, though they differ from Isoetes in their arborescent dimensions and 

 in their fruit being in the form of pedicellate cones, show so great an agreement with 

 them in the structure of their sporangia that their affinities with Isoetes is very close. 

 Of course the presence of microspores in the cones of Sigillaria is not absolutely 

 certain, but the evidence already accumulated points to their cones having been 

 heterosporous. 



Zeiller, in his interesting communication to which reference has been already 

 made,§ says, when discussing the affinities of Sigillaria : — " In conclusion, the 

 Sigillarise appear to me to deserve to be considered as constituting in the Lycopodiacese, 

 in some respects, an intermediate group between the Lepidodendron proper and the 

 Isoetes, on account of the affinities which they present towards the Isoetes in the 

 arrangement of their sporangia and probable mode of dissemination of the spores, and, 



* Goal Flora, pi. lxix. figs. 11-14. 



t Flora Sarcep.foss., Heft. i. p. 25, 1855. 



1 Rid., Heft ii. p. 1, 1857. 



$ Ann. d. Scienc. Nat., 6 e . ser., "Bot.," vol. xix. p. 278, 1884. 



