528 Sykes and Stiles .— The Cones of the Genus Selaginella . 
folded round its subtending sporangium (Fig. io, PL XLI)thanin any of the 
species yet described. The base of the sporophyll in 5 . flabellata is pro¬ 
vided with a dorsal ridge which is elongated at right angles to the long axis 
of the sporophyll, and projects freely downwards (Fig. 10, b and c, PL XLI). 
The ridge is strongly curved, and is a little more prominent in the median 
than in the lateral planes ; its ends turn upwards so that in a transverse sec¬ 
tion of the sporophyll at its base it is cut once, but higher up it is cut twice. 
It is traversed by an air cavity, and its surface is uncuticularized, while the 
rest of the sporophyll is covered by a remarkably thick cuticle (Fig. 10 e, 
Pl. XLI). The degree of development of the ridge is very variable, and in 
some cases it is almost entirely absent. The lowest sporophylls have 
generally a small dorsal projection (Fig. 10 d, PL XLI). 1 
In X. caulescens the sporophyll has a much smaller dorsal transverse 
ridge which does not project freely downwards (Figs. 11 a and 11 b , PL XLI). 
It is curved, and is a little less prominent in the median than in the other 
planes, so that to the naked eye it appears to constitute two small bulging 
projections. There is here no definite air cavity. 
The microsporangium is round or oval in all the species included 
in Type 4, and is never saddle-shaped. The line of dehiscence is along 
a slit placed much as in the more primitive species. 
The stalk of the sporangium of X. flabellata is composed of several 
rows of cells with strongly lignified walls (Fig. io<?, PL XLI); these 
are well developed even when the sporangium is still quite immature. 
In X. caidescens there is a row of cells with lignified walls which are 
strictly confined to the base of the sporangium stalk, and are much less 
prominent than in the other species. 
S. flabellata shows a tendency to variation in the number of the mega¬ 
spores. 2 In one sporangium two large and two small megaspores occurred ; 
in another there were one large spore, two smaller ones, and two very 
small ones. 
Type 4 b. X. Vogelil, like others of the dorsiventral species of Selagi - 
nella , has square cones which are fairly compact; in the young cone of this 
species the sporangia are entirely concealed. 
The cones are very small; each sporophyll is unusually long and so 
closely folded that in transverse section it appears to be V-shaped ; thus 
it protects efficiently its own subtending sporangium. There is no dorsal 
flap or ridge adapted for the protection of any other of the sporangia, and 
no air cavity is present in the sporophyll (Fig. 12, PL XLI). 
The epidermis of the sporangium stalk is strongly cuticularized, and 
1 See p. 525, footnote 2. .S'. Preissiana (Goebel, K., Organography, ii, p. 505 and Fig. 338) 
probably belongs to Type 4. 
2 Variation in the number of the megaspores in this and other species is recorded by Mitchell, G., 
(1910, pp. 24, 25). 
