744 PROFESSOR W. C. WILLIAMSON AND DR. D. H. SCOTT ON THE 
On the other hand, Fern sporangia are occasionally found among the fragments of 
Lyginodendron foliage, though never in actual continuity with it.* 
Two possibilities suggest themselves : 
1. It may be, that Lyginodendron was, as to its fructification, a true Fern 
(in spite of its anatomical peculiarities) and bore sporangia on its leaves; they 
might very easily have become detached, and the want of any evidence of continuity 
between sporangia and leaf would not be surprising. 
2. It is possible that our material consists entirely of young plants, in which case 
the absence of fructification is easily accounted for. 
On the whole, we incline to the latter view; if our specimens had often been 
fructifying ones, it is probable that sporangia, even though detached, would be much 
more commonly found than is actually the case. The few examples observed are 
easily explained by accidental admixture of foreign material. 
We think, therefore, that the whole question of fructification must be left open 
for the present. 
We shall not enter further into the consideration of affinities, until the genus 
Heterangiwm has been dealt with, for the two genera throw much light on each 
other and must be discussed together. 
IL.—HETERANGIUM, Corda. 
INTRODUCTION. 
The genus Heterangium was founded by Corpa in 1845, on a fragmentary speci- 
men from the Bohemian coal-measures. The first British specimens were discovered 
in 1871 among Mr. Grigve’s Burntisland fossils. This form was originally named 
Dietyoxylon Grievi, but in 1872 was placed in Corpa’s genus, and now bears the 
name of Heterangiwm Grievii, W1u1.t 
In addition to the Burntisland specimens, fossils which appear to be referable to 
the same species were discovered at a later date by Mr. Lomax, at Dulesgate, in 
Lancashire.{ 
In the mean time, a second species, in a marvellous state of preservation; had been 
discovered in the Halifax coal-measures. To this form the name of Heterangium 
tiliwoides, WILL., was given.§ 
A French species, Heterangium Duchartrei, B.B., originally referred to the genus 
Poroxylon, was discovered by M. Renautr, and shows a considerable resemblance to 
* See, for example, C.N. 1630, 1979, 1990. 
+ Wittiansoy, ‘ British Association Reports,’ 1871; “ Organization,” Part IV., 1872, pp. 394 and 404. 
¢ Wituiamson, “ Organization,” Part XVIL., 1890, p. 96. 
§ WitLiamson, “ Organization,” Part XIII., 1887. 
