8 STIGMARIA FICOIDES. 



am indebted to Mr. J. Hampden Barker for this sketch and for the careful measure- 

 ments which accompanied it. The greatest diameter of the specimen was rather 



Xylograph 2. 



more than 9 feet from the tip of root 1 to that of root 7. The shorter roots on each 

 side of this longer axis could not be traced, since they plunged deep into the side 

 walls of the mine. Whilst this specimen appears to subdivide into twelve roots 1 

 the division into four primaries is even less obvious than in Xylograph 1. 

 Though Mr. Binney's crucial line frequently exists, it is not a constant feature of 

 these matured roots. 



The above facts show that considerable differences exist in the length attained 

 by these primary roots before they subdivide into secondary ones; whilst the 

 Duckinfield tree demonstrates that their ultimate branches may extend to great 

 lengths with but little variation in their diameter. 2 



1 The division between the roots 10 and 11 is not very distinct, but the otherwise symmetrical 

 arrangement of the roots leaves little doubt that a division exists there. 



2 This fact is not unimportant since M. Eenault is disposed to recognise in such elongated 

 examples a distinct class of organs from those which dichotomise near the base of the stem. He says, 

 " Cette observation est difficilement explicable par l'existence des simples racines," ' Cours de 

 Botanique fossile,' premiere annee, p. 154. At p. 9 of his ' Etude sur les Stigmaria, rhizomes et 

 racines de Sigillaires,' he says, ' L'epaisseur considerable que conservent les racines principales 

 jusqu'a leurs dernieres sous-divisions, la grande regularite de la ramification, le mode de disposition 

 et la disarticulation des organes appendiculaires donnent aux Stigmaria un caractere tout par- 

 ticulier que ne se rencontre dans le systeme radiculaire d'aucun autre type vegetal, et Ton se 

 demande si ces curieux fossiles ne representeraient pas plutot des rhizomes que des racines. Dans ce 

 cas, les organes pris pour de radicelles et auxquels Goeppert attribue le nom de fibrilles, ne seraient 

 autre chose que des feuilles souterraines representant les feuilles rudimentaires appelees ecailles des 

 rhizomes ordinaires." 



I shall have to show on a later page that none of these statements are applicable to Stigmaria 

 ficoides. Subterranean rhizomes amongst the living Lycopodiaceas differ very little in structure from 

 the stems of which they are mere extensions. This is shown by the example of Psilotum triquetrum. 

 But Stigmaria differs wholly both from Lepidodendron and from Sigillaria in wanting the inner vascular 

 zone seen in both these genera, the etui medullaire of Brongniart, from which alone all the vascular 



