294 LYCOPODIALES 
subtended by leaves of the foliage type (Z. varium); while, on the other 
hand, leaves of the sporophyll type may develop no sporangia (Z. swbulatum, 
Phlegmaria). There may occasionally be alternating sterile and fertile 
zones (L. nummularifolium). Transitions from the fertile strobilus to the 
larger-leaved foliage shoot are frequent (ZL. nummudarifolium, subulatum, 
ophioglossoides, pinifolium, Phlegmaria). Thus the differentiation of the 
strobilus is one of external form rather than a rigid difference of intimate 
character. The converse conditions of Z. varium and L. subulatum show 
that the difference of size of sporophylls and foliage leaves is not due 
directly to correlation in the individual parts, but rather to the general 
condition of the shoot as a whole. 
The above groups, including fully one half of the living species of 
Lycopodium are now associated together under the sub-genus Urostachya' ; 
the characters assigned are not only those of the distribution of the sterile 
and fertile zones, but extend also to other features. The branching of 
the axis is almost, or entirely, absent in the simplest of the upright forms: 
in the trailing or pendulous forms it is more frequent. It is of the 
dichotomous type, and usually in planes successively at right angles. The 
roots arise primarily from the basal region of the axis; in no case is 
there a creeping monopodial axis, with adventitious roots arising along 
its whole length. In about half of the species there is no formal dis- 
tinction of sporophylls from the foliage leaves: where such a distinction 
exists the sporophylls still have a green colour, and as a rule an entire 
margin. The spores have a pitted surface, without external processes. 
These general characters indicate a natural grouping of species which are 
certainly the simpler living representatives of the Lycopod type. 
The second sub-genus, designated Ahopalostachya, includes the remain- 
ing species which are more differentiated than the first in many of their 
characters. The branching of the axis is only dichotomous in the younger 
parts, and becomes monopodial later, often with a well-marked main axis. 
All the species are ground-growing; a few are climbers. The upright 
species are freely branched (Fig. 143); in the creeping species the 
recumbent axis gives off upright branches, and is attached to the soil by 
successive adventitious roots; the fertile strobili are for the most part 
definitely marked off from the sterile region, and are often carried upon 
elongated stalks, which bear minute scale-leaves (Fig. 144). The differ- 
entiation of the sterile and fertile leaves is constant; the sporophylls are 
pale, often chaffy scales, with toothed, ciliate margin (Fig. 143 D, £), 
while the spores bear reticulate flanges or prickles on their outer wall. 
These characters collectively mark off Ahopalostachya as more differentiated 
than Urostachya. But it includes some species which approach the latter ; 
thus the three species associated as the zzundatum group show only slight 
differentiation of the strobilus from the vegetative shoot, while abortive 
sporangia are found at the base in L. taundatum. L. Drummondii even 
1See Pritzel, Engler u. Prantl, Wat. Pflanzenfam., i. iv., p. 591. 
