THIRD REPORT OF THE DIRECTOR I906 61 



Special attention to the examination of the very large Upper 

 Devonic " Lepidodendron " in the Museum — a specimen measur- 

 ing II feet, 6 inches in length and with the root complete. As 

 originally taken out this fine fossil had a length of 15 feet. Mr 

 White has submitted the following note concerning this tree. 



Archaeosigillaria vanuxemi Goepp. (sp.). This slab carries the 

 basal portion of one of the earliest representatives of the great 

 group of the Lepidophytes, a group of enormous extent and of 

 treelike proportions in the older Coal Period (Carbonic), though 

 survived now only by the relatively unimportant and humble 

 Lycopodiales, including the club mosses (''ground pines" and 

 "ground cedars") in the flora of today. The forerunners of the 

 Lepidophytes in the Devonic, found but rarely and in a very frag- 

 mentary condition, were very much smaller than their Carbonic 

 descendants from which they differed by certain systematic char- 

 acters. 



The stem here shown is extraordinary not only for its rarity, 

 relatively fine preservation, and large size as compared with other 

 Devonic plants, but also for the fact that it combines in one individ- 

 ual trunk some of the features which serve to characterize and 

 differentiate several distinct later lepidophytic groups. It represents 

 the type ancestral to these groups. 



The base of the stem is truncated, probably as the result of decay 

 of the main roots; but the small ribbonlike rootlets, articulated at 

 typical stigmarian areolate scars, are still in evidence at the ex- 

 treme butt. The latter is much dilated as the result of a very great 

 thickening of the bark, and possibly by the development of some 

 secondary (exogenous) wood in addition, so that the rows of leaf 

 cushions are widely separated and frequently displaced in a way 

 similar to that found in the base of some Carbonic sigillarian 

 trunks and even in certain old trunks of Lepidodendron. Traces 

 of leaf cushions are observable down to within 5 centimeters of the 

 bottom of the specimen. 



The stem rapidly contracts above the enlarged base and the num- 

 ber of leaf cushion rows, is, at the same time, greatly increased by 

 the intercalation of new series. In this portion of the trunk the 

 leaf cushions are sigillarian in form and they are placed in vertical 

 rows, each row occupying the median area of a longitudinal rib, 

 the cushions in the same row being separated by transverse grooves 

 across the rib in an arrangement characteristic of the Favularian 

 section of the Rhytidolepis group of the Carbonic Sigillariae. 



