GENERAL MORPHOLOGY 307 
outgrowths from the axis itself, which have been regarded as rudimentary 
rhizophores. It does not seem an undue strain of comparison to suggest 
that in this basal knot is still to be seen, on a minimal scale, a living 
representative of those larger growths known as the Stigmarian trunks. 
These would thus be in their nature indeterminate outgrowths of the 
hypocotyl, as are these rudimentary rhizophores; but like them, strictly 
localised in origin, instead of being dispersed over the branch-system, as 
are the rhizophores in most modern Se/aginellas. It is thus’ possible to 
bring the general morphology of Lefidodendron into relation to that of 
the modern Selaginella, a type which there is reason to believe itself 
dated from the Carboniferous period. 
On the other hand, there are obvious relations between the dendroid 
Lycopodiales and the living genus Jsoe¢es: this type has been found 
fossil in the Tertiaries, and back as far as the Lower Chalk, while in the 
Trias the curious fossil Plewromoia is represented: but there is no suffi- 
cient evidence of the genus Jsve/es having: itself figured among the earliest 
fossils. 
The plant of /sve¢es consists of a short upright axis covered by relatively 
large leaves (Fig. 155): the axis is usually unbranched, though bifurcation 
occasionally occurs, a fact that has its interest for comparison with the 
Lycopods.! The leaves are essentially of one type, with broad base and 
acicular upper part, while seated in a pit on the upper surface, at some 
little distance from the base, is the ligule. The leaves may be either 
sterile or fertile, and in some species there is a difference in size, the 
sterile leaves being the smaller. The plant is heterosporous. Where the 
leaf is fertile the large cake-like sporangium lies in a depression of the 
leaf-surface, between the ligule and the leaf-base, that region being 
elongated to accommodate it: in the sterile leaves it is shorter. An 
examination of the sterile leaves of “ Jacustyis (and Wilson Smith made 
similar observations in Z echinospora) shows that sporangia in various 
degrees of abortion may be found upon them: in some of these spores 
are developed, but in smaller numbers than the normal: other sporangia 
may remain quite small, and produce no spores. Dissections show that, 
in the majority of leaves that are apparently sterile, a rudimentary sporan- 
gium is really present in a normal position. It is stated that a regular 
seasonal sequence is followed in the distribution of the megasporophylls, 
the microsporophylls, and the foliage leaves: that the megasporangia are 
borne on the first or outermost leaves of each annual increment, then 
follow leaves with microsporangia, while the sterile leaves form the transi- 
tion from one year’s increment to the next. It is thus seen that in the 
distribution of its sporangia Jsvefes shows a condition similar to that of 
Lycopodium Selago, but that the various degrees of their abortion are 
better represented. It follows from the facts that after the embryonic 
stages are past—in which no sporangia are produced—the whole plant is 
1Solms Laubach, Bot. Zedt., 1902, p. 179. 
