Johnson — A Seed-bearing Irish Pteridosperm. 9 



factory in that it not only supports Kidston's identification of 8. Honinghnusi 

 as the foliage of Lyginodendron oldhamium, but shows also, by the evidence of 

 direct continuity, that Calymmatotlieca Stangeii is the fertile female frond of 

 Lijginodendron, and that it enclosed in its tuft of cupular lobes a seed most 

 closely allied to, if not identical with, the fully described Lagemstoma Lomaxi. 

 If this view be accepted, the synthetic reconstruction of Li/ginodendron old- 

 hamium, as an example of an extinct Palaeozoic Pteridosperm, is completed. 



A feature that strikes one in reading the accounts of the male and female 

 organs of these Palaeozoic Pteridosperms is the marked degree of divergent 

 differentiation already attained in the characters of the two. Theoretically 

 one would expect them to show, in some features common to both, signs of 

 their origin from a type represented in the sporangial sori of some primitive 

 fern. Yet the contrast between the male organs of the Crossotheca type and 

 the female ones represented by Lagenostoma shows that the differentiation 

 had already proceeded far in Lyginodendron. In this connexion our specimen 

 presents an interesting feature, reproduced in Plate III., fig. 5. In an other- 

 wise normal pinnule two of the segment-lobes have become elongated and in 

 all respects like the cupular lobes. These I regard as signs of commencing 

 fertility on the part of the pinnule in question, and also as indicative, if 

 further indication is necessary, of the foliar nature of the cupular lobes found 

 sui-rounding the seed. The seed itself, indeed (Plate III., fig. 3), might easily 

 pass for a cupular lobe on casual inspection, and is, in reality, I think, a foliar 

 lobe transformed into a seed — i.e. it is an ovule- or macrosporangium- 

 bearing foliar segment. Looked at iu this way the difference between 

 the male and female is not so great as appears to be the ease at first 

 sight. In the case of the male the pinnule becomes fertile and forms 

 five or six bilocular microsporangia on the underside of the expanded apex of 

 each of the transformed segments of the pinnule. In the female the five or 

 six segments of the fertile pinnule become ligulate, or flattened and ribbon- 

 like, and envelop more or less one lobe which becomes stouter than the others 

 and forms an ovule or macrosporangium. The enveloping lobes may fuse 

 more or less together to form the protecting eupule, but appear homologous 

 with the ovuliferous lobe. If this view be correct, there is nothing to 

 prevent the conversion of other cupular or foliar lobes into ovules, leading 

 to the occurrence of two or more ovules in one terminal rosette of the naked 

 branch of the rachis. There is, however, one difference which one finds so 

 frequently in plants, viz. an abundant development of the male organs, giving 

 many microsporangia and microspores, and a small development of the 

 female ; in this case, solitary macrosporangia or ovules, isolated, on branches 

 of the rachis. Both male and female sporangiophores are foliar in nature. 



SCIBNT. PBOC, E.D.S., VOL. XIII., NO. I. ^ 



