EXTERNAL MORPHOLOGY OF THE STEMS OF CALAMITES. 507 
On the External Morphology of the Stems of Calamites, with a Revision of 
the British Species of Calamophloios and Dictyocalamites of Upper 
Carboniferous Age. By E. A. NEWELL AnnER, M.A., Sc.D., F.L.S., 
and F. W. LAwrrELD, D.A.* 
(PLATES 23-25.) 
[Read 7th November, 1918.] 
CONTENTS. 
Page 
TV Tntroduction <i... cee serene ence +t Omini cena er Maine shore ciniicie © 507 
2, The External Morphology of Calamite Stems....... eene 508 
3. The Correlation of Specimens exhibiting the external features of 
certain stems with their pith casts .... eee 513 
4. A Systematie Revision of the British Species of Calamophioios and 
Dictyocalamites sisse. i ka ae r eene rnae e e 51 
5. Bibliography s+». seene. r i RE A TE 527 
Explanation of the Plates. .......ssseeererererreeerreererett" . 698 
1. /ntroduction. 
IwPnEssTONS or casts of the external features of Calamite stems are still 
very little known in comparison with the pith casts of the same plants. As 
fossils they are not only much rarer but usually more fragmentary than the 
medullary casts, and for this reason little attention has been paid to them 
hitherto. Examples of external impressions of these plants have been figured 
from time to time by various authorities, including Sturt, Weiss f, and 
Solms §, and, in quite recent years, especially by Jongmans || and Kidston f. 
In all four of the large monographs which we now possess on the 
‘alamites by Stur, Weiss, Kidston, and especially Jongmans, by far the 
greater number of the figures relates to pith casts. As a rule examples of 
both medullary casts and impressions showing the true external features of 
the stem are mixed together in confusion and are all referred to a common 
genus— Calamites. Neither from the generic nor the specific names 
employed, can one distinguish whether one is dealing with pith casts or 
with the rarer external surfaces of these stems. 
In the largest and most recent monograph of this genus, that by Kidston 
* Owing to the death of Dr. Arber the final revision of this paper has devolved entirely 
upon the junior author. 
+ Stur (1887). i Weiss (1876) (1885). $ Solms (1891) p. 317. 
| Jongmans (1911), Jongmans & Kukuk (1913). 
q Kidston & Jongmans (1915). 
LINN. JOURN.—BOTANY, VOL. XLIV, 
