Sporangium-bearing Organs of the Lycopodiaceae. 55 
similar to those of the elongated elements surrounding the stele in 
that and other species, may possibly represent another step in the 
reduction of what may once have been a small vascular bundle 
while in L. serratum, etc., we find an almost complete absence of 
cells with lignifled walls in the sporangium pedicel. 
(b.) Comparative evidence. If the series of species of 
Lycopodium is a reduction series, a more intelligible hypothesis 
can be constructed concerning the relations of this genus with 
recent and fossil Pteridophytes. It is impossible to produce 
definite evidence as to the direct ancestory of Lycopodium. Of the 
Lycopodites , l their obvious relations, we know so little that in most 
cases we cannot ascertain whether any given form is a Lycopodium 
or a Selaginella ; but there appear to have been no striking 
differences between this collection of species in the Palaeozoic Era 
and the Lycopodiums of to-day. 
It would not be difficult to derive such a plant as L. cernuum 
from Lepidodendron or one of its allies. For, even if Lepidodendron 
itself is more nearly allied to Isoetes, —as is suggested by the 
position of the sporangium, and the discovery of a ligule, a 
parichnos , 2 and sporangial trabeculae in both genera—it is still 
possible to suppose a comparatively close relationship to 
Lycopodium, in the sporophylls of which genus a parichnos is also 
generally present . 3 Perhaps the complex sporophyll present in the 
Rhopalostachya is sufficient for the protection of the young 
sporangia of such small cones , 3 from too great evaporation, and the 
mucilage once secreted by the ligule 4 is now no longer necessary. 
It is conceivable that some such theory may also explain the 
absence of the ligule in Spencerites, which may then be brought 
into connection with the above genera. It has been already stated 
that the sporangium in this plant is attached to the stalked 
sporophyll in a position which is recalled by the tangentially 
placed sporangium of Lycopodium cernuum, etc., while the small 
lump of tissue or “ ventral lobe ” found between the sporangium 
and the distal end of the sporophyll recalls the ligule of Lepidoden¬ 
dron 5 ; it is possible to regard Spencerites as an ancient connecting 
link between the old Lepidodendra and the Lycopodiums, 
1 Goldenburg, 1855; Solms Laubach, 1891, p. 186; Engler and 
Prantl, Teil I., Abt. 3, p. 715. 
2 Hill, T. G., 1906 ; Potonie, ’99, p. 239 ; Weiss, 1907. 
3 c.f., Worsdell, 1902. 
3 Halle, 1907 : Gibson, 1896. 
6 cf. also Araucarias, Seward and Ford, 1906. 
