6i0 STEVENSON— FOR^IATION OF COAL BEDS. [November 3. 



found frequent occurrence of Stigniaria in situ at Commentry. One 

 notable discovery was that of a stump, whose roots spread out in 

 an area of 6 meters diameter and retained their minute appendages. 

 According to Renault, the branches extended farther but they could 

 not be followed. Fig. 46, copied from Renault's description, justi- 

 fies Potonie's remark that, if this be a transported tree, one must 

 believe that it and the fine mud enclosing it had been transported 

 together and deposited in the original position. 



Schmitz^'^' examined ^,2, erect stumps exposed in the roof of the 

 Grande Veine of the Liege basin. The coaly crust, sometimes one 

 centimeter thick, and the scars suggest that the plants are Sigillaria. 

 The stumps are in a space of 2 by 95 meters, giving for each plant 

 5.6 scjuare meters, a condition favorable to the belief that they are 

 in loco natali. But he found that the trunks are all cut ofif at the 

 coal bed ; most of them show the enlargement belonging near the 

 roots, so that one cannot suppose that the trees extended downward 

 through the coal to the mur. On the other hand, the transition from 

 coal to sterile rock above is barely one centimeter of coaly clay, so 

 that they could not have been rooted in the toit. The laminae of 

 this faux-toit contain many impressions of twigs of lycopods and 

 Eqiiisctitcs. Four of these pass under the bases of four erect 

 trunks. This led Schmitz to think it impossible that the trunks 

 were in loco natali ; for if those four were not, there is no reason to 

 suppose that the others were. To explain the condition, one must 

 invoke transport. But, in a later paper to be considered in another 

 connection, he gives the results of a more detailed study, which led 

 him to recognize that the abrupt cutting ofif at the base was due to 

 slips, which explained the presence of plant impressions under the 

 ends of the free trunks. 



Grand' Eury^°* summed up the results of his long study in a 

 memoir presented at the Paris meeting of the Geological Congress, 



^"^ G. Sclimitz, " Un banc a troncs-debout aux charlionnages du Grand- 

 Bac," Bidl. Acad. Roy. de Belgique, 3me Ser., Vol. XXXI., 1896, pp. 261-264. 



^*' C. Grand' Eury, " Sur les tiges debout, les souches enracinees, des 

 forets et sous-sols des vegetations fossiles et sur le mode et le mecanisme 

 de formation de couches de houille du bassin de la Loire," C. R. Cong. Geol. 

 Intern., 1900, Vol. L, pp. 523-530. 



238 



