Sykes and Stiles .— The Cones of the Genus Selaginelia. 533 
Summary. 
There have now been described in this genus four main types of 
sporophylls. 
I. In S.pumila , 5 . rupestris , an unknown species, and probably also 
vS. Lyallii, the sporophyll has a well-developed dorsal flap extending freely 
downwards, and protecting the young sporangium immediately below it. 
Two of the species have radially arranged leaves, and are presumably 
among the more primitive members of the genus. 
II. In S', spinosa , the only other radial species examined, there is 
nothing which can certainly be compared with this free dorsal flap. A slight 
dorsal swelling is present, occupied by an air cavity ; it is possible that this 
may represent the reduced remains of such a flap. In this species the 
sporophyll is flat and the sporangium exposed. 
III. In A. helve tic a, one of the dorsiventral species, there is a well- 
developed dorsal projection which is however not free but decurrent. It is 
especially prominent in the young cone where the two alternating sporangia 
of the whorl below are appressed against it. It is suggested that it may be 
homologized with the free dorsal flap in S.pumila , here fused with the stem. 
IV. The species placed in Type 4 form a series, in which the dorsal 
outgrowth, which originally served to protect the sporangia below, is 
gradually reduced and lost, while at the same time each sporophyll more 
and more completely enfolds and protects its own subtending sporangium. 
In S. jlabellata there is a transversely elongated dorsal projection the 
median portion of which extends freely downwards ; in .S. catdescens the 
free median portion is lost, and only a small curved ridge is left; in A. Vogelii 
and A. apus all signs of a dorsal projection at the base of the sporophyll are 
lost. 
The following table is meant to illustrate this comparison of the sporo¬ 
phylls, but is not intended to indicate phylogenetic relationships:— 
S. pumila ) free dorsal flap, 
'S. rupestris $ sporophyll a little folded. 
S. spinosa 
small dorsal swelling, 
flat sporophyll. 
S.jlabellata 
dorsal ridge with 
free projecting portion, 
sporophyll folded. 
S. Helvetica 
large decurrent dorsal swelling, 
sporophyll a little folded. 
S. caulescens 
small dorsal ridge with 
no free portion, 
sporophyll more closely folded. 
S. Vogelii 
no dorsal projection, 
sporophyll completely 
enfolding sporangium. 
