Seward . — A Contribution to our 
robustum and Cycadoxylon Fremyi. In the absence of more 
complete specimens, it is impossible to decide which of these 
generic names shall be adopted 1 ; but the Arran plant may, 
I believe, be regarded as closely allied to Lyginodendron 
Oldhamium and Cycadoxylon Fremyi. The figure of a trans- 
verse section of Lyginodendron anomalum given by Williamson 
in his Memoir IX, PL XXV, Fig. 90, does not bear so close 
a resemblance to Lyginodendron robustum as is apparent in 
another section recently cut from the same specimen and 
now added to the Williamson Collection. In this section 
the broad medullary rays and bands of tracheids are more 
regular in their arrangement, and the section as a whole 
exhibits a striking similarity to that of Lyginodendro 7 i 
robustum. A small portion of this section is shown in PL VI, 
Fig. 13 ; in some of the bands of tracheids the individual 
elements are occasionally cut across obliquely, but on the 
whole the structure is like that shown in the figure. 
Without attempting to give a specific diagnosis, we may 
briefly summarize the more important characteristics of the 
specimen for which the name Lyginodendron robustum is 
suggested, and which has hitherto been spoken of as * Nield's 
specimen.’ The centrifugal wood is composed of reticulately- 
pitted tracheids somewhat smaller in diameter than those of 
Lyginodendron Oldhamium ; the medullary rays are rather 
broader, and there is a more regular continuous zone of 
centripetal xylem than in Lyginodendron Oldhamium. In 
the latter plant this internal development of xylem is found 
to vary considerably in amount in different regions of the 
same transverse section. In the transverse section 1885 E 
(Williamson Collection), the ‘anomalous wood’ is well shown, 
but internal to one of the primary xylem-strands it is absent. 
This particular group of xylem is seen to be in direct 
continuity with the external centrifugal wood in such a 
1 In addition to the sections in the Williamson Cabinet (No. 1208 and three 
others), there is a somewhat larger tangential section, apparently from the same 
specimen, in the Binney Collection (Cambridge). The original specimen is in the 
Hunteiian Museum, Glasgow University. 
