lO 8cie7itific Proceedings^ Eoyal Dublin Society. 



The male pinnule of Kidstoii's Crossotheca Honinghausi is homologous with 



the female piunule of Cali/mmatotheca Stangevi. They both represent 



Lyginodendron oldhamium in a fertile state. 



In Plate JII., fig. 6, 1 have attempted to show by means of diagrams what 



appear to me to be the homologies of the sterile male and female parts of 



Lyginodendron. Bach slightly stalked segment of the sterile pinnule {a) has 



in the male {h) concentrated its energj', not into tlie formation of a broad 



lamina, but of a naked stalk, carrying on its discoid tip a group of pendulous 



bisporangiate synangia, i.e. bilocular pollen-sacs, {Crossotheca). In (c) the 



condition is com2:>arable to that in [h) ; but only one of tiie terminal lobes is 



fertile. This becomes the seed; and the other lobes (though potential seeds ?) 



form a protecting envelope to the fertile lobe. On this interpretation the 



bilocular pollen-sacs and the seed are homologous with one another and with 



the pinnule segments or their lobes. 



Goeppert, in his " Die Grattungen der fossilen Pflanzen," describes and 



figures a species of Sj-yhenopteris as 8. spinosa, characterized by elongated 



foliar lobes similar to those I have just mentioned as present in our specimen 



of L. oldhamium. The digitiform processes are not found on all parts of the 



frond, and Goeppert explains this by saying they had there been already 



broken off. My explanation is that 8. spinosa is really a 8phenopteris in a 



state of commencing fertility. Von ZitteP states that Lesquereux^ was 



the first to observe the mode of fructification typified in C. Stangeri, in the 



Carboniferous fern Staphi/lopteris. Stur described the star-shaped bodies as 



indusial lobes, within wliich the receptacle of sporangia could not be seen. 



Lesquereux, von Zittel, Zeiller, and Renault all described the lobes as the 



actual sporangia. I am of opinion that Hugh Miller' had the bodies before 



him in 1857 in Parka decipiens of Fleming, when, treating them as of an 



unknown nature, he compared their appearance to that presented by the rayed 



calyx and fruits of a crushed bramble. It would be of interest if the specimens 



could be re-examined in the light of the evidence of the last few years on 



Pteridosperm seeds. 



SuMMAiiy. 



1. The Palaeozoic group of Pteridospermece flourished in Ireland. 



2. The Museum specimens of 8phenoi)teris Honinghausi confirm the view, 

 if such confirmation is necessary, that this "Fern" is in reality the foliage 

 of the Pteridosperm Lyginodendron oldhamium, Willm, {Crossotheca Honing- 

 hausi, Kid St.). 



' K, A. von Zittel: Traite de Paleontologie, ii., p. 106. 



- L. Lesquereux ; Palaeontology of Illinois, vol. iv. 



* Hugh Miller : " Testimony of tlie Rocks," 1S67, fig. 121, p. 443. 



