STRUCTURE OF FOSSIL PLANTS 69 



number of palaeozoic fructifications must be considered 

 in the next chapter. 



CHAPTER VII 



MINUTE STRUCTURE OF FOSSIL PLANTS— DIFFER- 

 ENCES FROM LIVING ONES 



We have seen in the last chapter that the main 

 morphological divisions, roots, stems, leaves, and fructifi- 

 cations, were as distinct in the Coal Measure period as 

 they are now. There is one structure, however, found 

 in the Coal Measure fossils, which is hardly paralleled 

 by anything similar in the living plants, and that is 

 the fossil known as Stigmaria. Stigmaria is the name 

 given, not to a distinct species of plant, but to the large 

 rootlike organs which we know to have belonged to all 

 the species of Lepidodendron and of Sigillaria. In the 

 frontispiece these organs are well seen, and branch away 

 at the foot of the trunk, spreading horizontally, to all 

 appearance merely large roots. They are especially 

 regularly developed, however, the main trunk giving 

 rise always to four primary branches, these each dividing 

 into two equal branches, and so on — in this they are 

 unlike the usual roots of trees. They bore numerous 

 rootlets, of which we know the structure very well, as 

 they are the commonest of all fossils, but in their in- 

 ternal anatomy the main "roots" had not the structure 

 which is characteristic of roots, but were like stems. In 

 living plants there are many examples of stems which 

 run underground, but they always have at least the 

 rudiments of leaves in the form of scales, while the 

 fossil structures have apparently no trace of even the 

 smallest scales, but bear only rootlets, thus resembling 

 true roots. The questions of morphology these struc- 

 tures raise are too complex to be discussed here, and 



