306 
R. C. McLean. 
I —Lagenostoma Lomaxii (Plate V). 
The gametophyte generation of Pteridospermic plants is known 
in a variety of cases. In some, merely distorted remains of pro- 
thalloid tissues have been found, which afford little clue to their 
original arrangement. 
In Stephanospermum , x however, where “ cytological ” preserva¬ 
tion is unusually perfect, the prothallus has accordingly been found 
in a state bordering on entirety, showing clearly remains of the 
archegonia in their natural position. Many seeds described by 
Brongniart 2 from the Carbonifer#us and Permian of France —as also 
specimens of the seeds of Cordaites —contain the endosperm and 
archegonia in a wonderful condition of preservation. The subject 
of the present description has not hitherto exhibited any such 
structures, and any remains of megaspore tissue preserved at all 
have been vague. 
The present specimen is a transverse section of the above 
seed, circular in outline, and bounded by the dark-brown testa 
with its two concentric bands ; the palisade on the outside, and the 
prosenchymatous hand on the inside, are fairly conspicuous. In the 
centre is the gibbous mass of fragile-looking tissue which represents 
the prothallus, lying rather to one side of the section, and entirely 
free from contact with any of the peripheral structures. (See 
Plate V). 
In a memoir which was published in 1904, Oliver and Scott 3 
described in detail a complex seed which had been discovered, in 
the first instance, by Williamson, although it was left by him 
undescribed. In bis manuscript catalogue, Williamson named this 
seed Lagenostoma Lomaxii , classing it with his two other species 
of that genus (L. ovoides and L. physoides) already published in his 
eighth memoir. 4 
The seed was referred by Oliver and Scott to Lyginodendron, 
on the basis of many features of anatomical agreement with the 
vegetative organs known to belong to the plant whose stem bears 
that name. 
Since the publication of their description, a fructification 
1 Oliver. “Trans. Linn. Soc., Bot.”, Vol. VI, 2nd Series, Part 
VIII, 1904. 
2 Brongniart. “ Recherches sur les graincs fossiles silicifies.” 
Paris, 1881. 
3 Phil. Trans., Ser. B, Vol. 197, 1904, pp. 193—247. 
4 “Organisation of Fossil Plants of the Coal-Measures,’’ Part 
VIII, Phil. Trans., 1877. 
