HICK AND CASH : AFFINITIES UF LEPIUODENDRON. 317 
assess tlieir morphological and taxonomic significance. In venturing 
to undertake the task of doing so, we have endeavoured throughout 
to present as facts only such as seem to be well established, and to 
maintain a sharp distinction between the facts and the conclusions 
we suggest as deducible therefrom. It need scarcely be said that the 
researches of Williamson have furnished us with nearly all the 
materials required for the descriptive part of this paper, but care has 
been taken to verify the statements made, by an appeal to actual 
specimens and preparations, wherever these were to be obtained. 
For this part of the work we have been greatly inde})ted to Messrs. 
Spencer, Binns, and Lomax, who have kindly allowed us to examine 
their specimens of Lepidodendron and compare them with those in 
our own cabinets. In addition to this we have profited* very largely 
by the kindness of Prof. Williamson himself, whose readiness to 
impart information on all occasions and in any way, deserves hearty 
and sincere recognition. In saying this, however, we must add, that 
in no way is he to be held responsible for anything herein contained 
which goes beyond the facts and conclusions put forward in his own 
publications. 
With respect to Lycopodium and /Selaginella, no botanist is 
unfamiliar with the details of their organization and structure, but 
we have deemed it advisable to summarise the fundamental and 
characteristic features of the stems, in order to give point to the 
comparison made with that of Lejndodendron. 
It has not been thought necessary to deal Avith the roots, leaves, 
and fruits of Lepidodendtvn with the same fulness as in the case of 
the stem, nor from our limited knowledge would it have been possible 
to do so. At first sight, it might seem that this would vitiate to 
some extent the conclusions we have attempted to draw as to its 
systematic relations with Lycopodium and Selaginella. Further 
reflection will show however that such is hardly likely to be the case. 
As regards roots, it is well known that in existing plants there is 
great uniformity in structure, even in groups that are widely separated 
and that root characters are seldom used as taxonomic distinctions. 
From the systematist's point of view leaves are more valuable, espe- 
cially in the distinction of genera and species. But in the distinction 
