BIOK : SOME RECENT ADVANCES IN BRITISH PALiEOBOTANY. 53 
carried as near completion as the specimens at present to hand will 
permit. The Memoir itself is not yet available, but its great import- 
ance is obvious from the abstract which has already appeared in the 
Proceedings." 
With respect to the affinities of these plants, the authors of the 
Memoir have arrived at most interesting and important conclusions, 
which cannot be passed over \vithout at least a brief reference. 
Students of pala^obotany ^Hill remember, that Williamson's earlier 
view was, that both genera belong to the Ferns. In accordance with 
this, he included them in the third part of the General, Morpho- 
logical, and Histological Index to his Memoirs,t which deals with 
Ferns, and pointed out that they approximate so closely to one 
another, in their structure, as to convince him that they both belong 
to the same division of the Fern family. The new investigations 
have led to an important modification of this view, and he and Dr. 
Scott are now of opinion that " the evidence afforded by the vege- 
tative characters " of Lyginodendron and Heterangium, " clearly 
points to a position intermediate between Ferns and Cycadese." It 
is admitted, in the abstract above-mentioned, that the leaves of 
Lyginodend/i'on, and probably those of Heterangium also, are unmis- 
takably Filicinean, but on the other hand it is pointed out that the 
structure of the stems is very suggestive of Cycadean affinities. After 
discussing the possible affinities with various groups of Ferns, the 
view finally suggested by the authors is, that the two genera " are 
derivatives of an ancient generahsed race of Ferns, from which they 
have already diverged considerably in the Cycadean direction. Of 
the two genera, Heterangium appears to be geologically the more 
ancient, and certainl} stands nearer to the Filicinean stock. Lygino- 
dendron, while retaining conspicuous Fern-like characters, has 
advanced much further on Cycadean lines." From this brief refer- 
ence it will be obvious that in this Memoir we have the record of an 
important increase of our knowledge of these two interesting types of 
Carboniferous plants, and it is not impossible that it may be the 
starting point for a further advance at an early date. 
* Proc. of the Royal Soc. , vol. 58. 
t Mem. and Proc. of the Manch. Lit. and Phil. Soc, 4th ser., vol. viii., 1893-4. 
