256 LYCOPODIALES [CH. 



and the ligule-pit is usually absent. The leaf-scar shown in 

 fig. H is 1'2 ram. broad and 1-4 mm. in height. The large 

 collection obtained during the visit of a Swedish expedition to 

 Bear Island in 1898 under the leadership of Dr Nathorst has 

 materially increased our knowledge of this ancient type. The 

 form of the leaf-scars varies according to the age of the branch 

 and their disposition is far , from constant even on the same 

 specimen; in some cases the scars are in fairly regular 

 whorls (fig. 212, G ; an Irish specimen) while in others they are 

 in regular spirals. This irregularity of arrangement, which is 

 well illustrated by Nathorst's figures of Bear Island and Irish 

 specimens, finds its counterpart, though in a less marked form, 

 in recent species of Lycopodium, e.g. L. Selago. Partially 

 decorticated stems may present a superficial resemblance to 

 Calamites, the fissured bark simulating the ribs of a Calamitean 

 cast. Such stems,- as Nathorst has pointed out, were mistaken 

 by Heer for Calamites radiatus. The smaller branches are 

 characterised by a smooth surface, and older shoots resemble 

 Bothrodendron minutifolium in the presence of fine vertical 

 lines. The preservation of only one pit on the leaf-scars of 

 many examples led authors to conclude that the species is 

 peculiar in this respect, but Nathorst has shown that in more 

 perfectly preserved specimens each leaf-scar bears three small 

 dots. A specimen from Ireland in the British Museum^ illus- 

 trates the dichotomous branching and the longitudinal wrinkling 

 of the bark ; the leaf-scars are 2 mm. broad and 2'5 mm. deep. 

 Nathorst'' has described some examples in which the leaf- 

 scars occur on the lower instead of on the upper end of the 

 leaf-cushions ; these and other specimens with obscure surface- 

 features he suggests may be underground axes, comparable 

 in habit with Stigmaria though not identical as regards 

 details. It is pointed out that the absence or scarcity of 

 Stigmaria in the Bear Island beds renders it unlikely that 

 Bothrodendron bore typical Stigmaria branches. F. E. Weiss* 

 has recently described root-bearing organs possessing primary 

 xylem identical with that of Bothrodendron Timndum. ; while 

 closely resembling Stigmaria ficoides in certain anatomical 

 1 No. 52524. 2 Nathorst (02) PI. x. figs. 4, 5. ' Weiss, P. E. (08). 



