50 
M. G. Sykes. 
appear certain which of the two great divisions should contain this 
interesting group, whose half-way position is confirmed by a 
knowledge of embryology and the gametophyte, and in some 
ways it would seem more suitably placed in a division by itself. A 
striking link between it and the Urostacliya is found in L. volubile, 
whose systematic position has been fully discussed. 
In the Rhopalostachya it has seemed reasonable, in view of the 
obviously simpler nature of the Clavata to place them belore the 
Cernua, but it is not therefore supposed that the two groups are 
necessarily connected, and indeed, other considerations appear to 
render it probable that the two groups may represent separate 
lines of development, 1 both connected with L. inundatum. 
Text-figs. 7 and 8 represent longitudinal sections of species of Cernua. 
and Clavata , in which groups the sporangium is not axillary but is borne on 
the stalk of the [peltate sporophyll. IX. (L. clavatum), shews the large 
archesporial pad (x) of that species. X. is L. laterale. Fig. 8, XI. shews 
two sporophylls of L. cernuum. In each case oblique shading indicates 
mucilage cavity, and cross-hatching or dots=lignified cells in sporangium 
pedicel, d=line of dehiscence. 
V.— Theoretical Considerations. 
It has been shown that the sporophylls of the various species 
of Lycopodium can easily be arranged in a series of increasing com¬ 
plexity ; considerable difficulty is felt, however, when an attempt is 
made to decide which end of the series is the more primitive. It 
1 Engler and Prantl, l.c. 
