(35) 



as the plants of the earlier periods are low in the scale of 

 life, consisting of thallophytes and pteridophytes and plants 

 of uncertain botanical determination, while those which 

 appear in the successively later periods are of successively 

 more complex types, represented by cycads, conifers and 

 both monocotyledonous and dicotyledonous plants closely 

 related to our living flora. 



The series of exhibits begins in the first case to the left as 

 one enters the east wing of the basement. The sequence of 

 the specimens in the wall cases corresponds to that of the 

 floor cases. 



In the first floor-case may be seen representatives of Eozoic 

 and Palaeozoic Time : Laurentian, Cambrian, Lower Sil- 

 urian, Upper Silurian, Devonian, and Carboniferous Periods. 

 At the north end are specimens of graphite of eozoic age 

 and of anthracite and bituminous coal of carboniferous age, 

 showing the transformation of vegetable matter into the ulti- 

 mate condition of pure carbon in the form of graphite or 

 "black lead" in the oldest rocks. Many of the specimens 

 in this case, classed as algae, are of uncertain botanical 

 relationship, as the structure of the primitive plants was not 

 well adapted for preservation as fossils. For example, some 

 organisms appear as mere filamentous strips of graphite in 

 white limestone, without any trace of the original structure 

 remaining, while others may be seen as casts and impressions 

 which closely simulate in general appearance different parts 

 of the sea-weeds now existing. In this series of problematic 

 fossils are also included a number of forms at one time 

 definitely classed as plants but now by some assumed to be of 

 animal or inorganic origin ; namely, Scolithus, which may be 

 caused by worm burrows ; Phylofisis, which may be a coral ; 

 Plumalina, which may be a hydroid ; Dendrofihycus, which 

 may be current-markings ; and Dictyolites, which are most 

 likely sun-cracks. All of these, however, have at one time 

 or another been definitely regarded as the remains of marine 

 plants and were originally so described and classified. 



In this case are also the remains of the earliest fern-plants 



