STIGMARIA 241 



the arrangement is just the same ; thus in the Clayton 

 specimen shown in Fig. 85, the stump of the stem is 

 more than 4 feet in diameter, while in another figured 

 by Williamson in his Monograph it only measures 

 6 inches. The angle at which the Stigmarian roots 

 pass off from the stem is variable. Sometimes they 

 take a nearly horizontal direction from the first '; in 

 other cases they first strike sharply down at an angle 

 of 50° or 60°, and only begin to take a more horizontal 

 course at some distance from the main trunk. 



The Stigmarian roots, as mentioned above, are 

 especially abundant in the clay underlying the coal- 

 seams, to which the name " Stigmarian clay " has been 

 given by English geologists ; they are, however, by 

 no means limited to this position. The conditions 

 must often have been more favourable for the pre- 

 servation of these underground organs than for that 

 of the aerial stem ; hence it is not surprising that in 

 some Carboniferous beds on the Continent, Stigmariae 

 are found without any corresponding remains of Sigil- 

 laria or Lepidodendron. It is still uncertain whether 

 Stigmaria when living ever occurred except in con- 

 nection with aerial stems. The Stigmaria, with its 

 appendages, manifestly performed the functions of a 

 root, taking up food from the soil. A rich soil seems 

 to have suited it, for the Stigmarian rootlets burrowed 

 in every direction through the mass of decaying vegeta- 

 tion which formed the organic material of the calcareous 

 nodules. They occur in countless numbers, crowded 

 together and penetrating every kind of vegetable 

 fragment — stem, leaf, root, or cone, so that the first 

 lesson a beginner has to learn, in studying the 



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