• 2 4 o STUDIES IN FOSSIL BOTANY 



rightly identified as Lepidodendron. Other cases, how- 

 ever, observed in Germany and in England, seem to 

 leave no doubt that the Stigmariae formed the subter- 

 ranean organs of Lepidodendron as well as of Sigillaria. 

 It is not even possible to distinguish specifically 

 between those of the two genera ; the name Stigmaria 

 ficoides does duty for both, and though other species 

 have been distinguished, we are rarely able to correlate 

 their diagnostic characters with those of the stems. 

 One or two special cases, on which rather more light 

 has been thrown, will be mentioned after the common 

 " species " has been dealt with. In the meantime, we 

 may take Stigmaria ficoides as representing the " roots " 

 of various Lepidodendra, as well as of various Sigillariae 

 of the ribbed division. 



The mode of connection between the Stigmaria 

 and its Sigillarian or Lepidodendroid stem has been 

 shortly noticed above (p. 206, Fig. 85). This has now 

 been observed in a great number of specimens, and 

 the main features appear to be constant. There is 

 never a tap-root forming the direct downward continua- 

 tion of the vertical stem ; the Stigmarian roots are 

 always given off laterally from the base of the stem, 

 and there are always four of them to start with, the 

 four occupying at their attachment the whole cir- 

 cumference of the trunk, which ends abruptly between 

 them ; its under surface is marked by a cruciate 

 furrow, corresponding to the lines of junction of the 

 Stigmarian roots. Each of these main roots forked 

 at least twice, and if the first dichotomy took place 

 very near the base, their number may appear to be 

 greater than four. Whether the stem be large or small, 



