200 Sellards— Fronds of Crossotheca and Myriotheca. 



Some of the larger spores have granular bodies within or cling- 

 ing to them, which show a dark spot at the center and some- 

 thing of the structure of concentric starch grains. 



The spores from a large number of fronds of two species 

 have been examined in order to iind whether or not there were 

 indications of more than one kind of spores. The species 

 studied were Pecopteris {Ptychocarpiis) unita Brongn., and 

 the form referred doubtfully bj Lesquereux to P. villosa 

 Brongn.,* which probably belongs to the Asterotheca division 

 of Pecopteris. Both species are extremely abundant at Mazon 

 Creek, and the sporangia-bearing fronds numerous. The spores 

 of P. villosa are small, measuring only -013 to -016™"^, smooth 

 and spherical. The exospore is very thin. The spores of the 

 European examples of P. unita have already been made 

 known by Renault.f The spores of the specimens at hand are 

 •016 to •018°'"' long, and -010 to •OH wide, being elongate or 

 bean-shaped when seen from the side. The exospore is thick 

 and smooth. The three radiatins^ lines at the apex can be seen 

 on some spores. As in other Marattiaceous ferns, the spore 

 output to the sporangium in both species was evidently very 

 great. The spores from many specimens of both species and 

 from various parts of the same specimen present no differences 

 in structure, size, or sculpturing, that could be interpreted as 

 indicating two kinds of spores. It is, therefore, practically 

 certain that both were homosporous, and this is exactly what 

 might be expected in typically Marattiaceous ferns. The fact 

 is of interest in connection with Renault's paper referred to 

 above, in which unusual conditions are observed in one of the 

 European species of Pecopteris. The fern described by 

 Kenault, which is of the Asterotheca division or sub-genus of 

 Pecopteris, has one set of spores which are smooth and marked 

 at the apex by three radiating lines. These are considered 

 megaspores. In the same sorus, and possibly in the same spo- 

 rangium, are other spores of about the same size, thought to be 

 microspores, which lack the lines at the apex and show struc- 

 tures interpreted as the mother cells of antherozoids. 



The second paper by the same author describes somewhat 

 similar appearances in Parherioidea. The megaspores are 

 smooth and show the triradiate lines at the apex. The micro- 

 spores, found in the same sporangium, lack the lines, and are 

 sculptured with a polygonal network. 



The three radiating lines are seen on the spores of all the 

 ferns examined by the writer, when viewed from the apex, and 



* According to Mr. Eobert Kidston, Fossil Flora of the Eadstoek Series, 

 Trans. Eoy. Soc. Edinburgh, vol. xxxiii, Part II, 1886-7, p. 37, P. villosahas a 

 doubtful existence, having been established in all probability on a villous 

 specimen of P. oreopteridia or a closely related species. 



f Bassin Houiller et Permien d'Autun et d'Epinoe, Pt. II, p. 10. 



