STIGMARIA 259 



instead of on the outer side only, as in S. ficoides. In 

 passing through the cortex these bundles are connected 

 with groups of reticulate tracheides, which probably 

 served for water-storage. 1 If this Stigmaria is rightly 

 attributed to Bothrodendron mundum, of which Mr. 

 Watson has now described the cone, that plant will 

 become the most completely known of the Palaeozoic 

 Lycopods. 



3. Morphology. — It only remains to consider very 

 briefly the morphological nature of Stigmaria and its 

 appendages. If we call Stigmaria a " root," it is 

 chiefly on physiological grounds that the term is used. 

 The main axis of Stigmaria ficoides has in no respect 

 the structure of a root ; in fact, this species, in the 

 absence of centripetal wood, departs from typical root- 

 structure more widely even than the aerial stems 

 themselves. Other forms of Stigmaria, though they 

 may possess centripetal wood, are no more root-like 

 in structure than the Sigillarian stem. The arrangement 

 of the appendages (which, in the rare cases where the 

 growing end is preserved, are found to have converged 

 to form a kind of bud at the apex of the main 

 Stigmarian axis) is unlike that of rootlets, nor does 

 their origin seem to have been endogenous. 



On the other hand, the appendages agree so exactly 

 in structure and in the dichotomous mode of branching 

 with the monarch roots of the allied recent genera 

 Isoetes and Selaginella? that it seems impossible to 



1 Weiss, " A Stigmaria with Centripetal Wood," Ann. Bot. vol. xxii. 1908. 



2 In the Stigmarian appendages the position of the phloem, which 

 appears to have formed an arc on the side of the strand remote from the 

 protoxylem, agrees exactly with that in the roots of these recent plants. 



