294 LYCOPODIALES 



subtended by leaves of the foliage type (L. varium)\ while, on the other 

 hand, leaves of the sporophyll type may develop no sporangia (L. subulatum> 

 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 (L. nummularifolium, subulatttm, 

 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 L. 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 x ; 

 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 Rhopalostachya, 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, E), 

 while the spores bear reticulate flanges or prickles on their outer wall. 

 These characters collectively mark off Rhopalostachya as more differentiated 

 than Urostachya. But it includes some species which approach the latter ; 

 thus the three species associated as the inundatum group show only slight 

 differentiation of the strobilus from the vegetative shoot, while abortive 

 sporangia are found at the base in L. inundatum. L. Drummondii even 



1 See Pritzel, Engler u. Prantl, Nat. Pflanzenfam. , i. iv. , p. 591. 



