32 Notices of Memoirs — Vegetation of the Coal Period . 



conditions which prevailed during that period in the earth's history 

 that was par excellence the age of coal production. The minute^- 

 examination of petrified tissues has rendered possible a restoration 

 of the internal framework of several extinct tj'pes of plant-life, and 

 has carried us a step further towards the solution of evolutionary 

 problems. It is possible, even with our present knowledge, to 

 make a limited use of anatomical structure as an index of life- 

 conditions, and to restore in some degree from structural records the- 

 physiological and physical conditions of plant-life characteristic of 

 the close of the Carboniferous epoch. 



(1) Evidence furnished hy the Coal-period Floras as to Climatic and' 



other Physical Conditions. 



The uniformity in the character of the vegetation has no doubt 

 been somewhat exaggerated ; e.g., the Glossopteris flora of Australia, 

 South Africa, and South America. The existence of botanical 

 provinces in Upper Palaeozoic times. 



A comparison of the Coal-period vegetation with that of the 

 present day as regards (i) the relative abundance of certain classes 

 of plants, (ii) the geographical distribution of certain families of 

 plants during the Carboniferous epoch and at the present day. The 

 importance of bearing in mind the progress of plant-evolution as 

 a factor affecting the consideration of such comparisons. The 

 possible existence of a Palceozoic Mountain flora of which no 

 records have been preserved. 



(2) The Form, Habit, and Manner of Occurrence of Individual Plant& 



as Indices of Conditions of Growth. 

 Comparison of Calamites and horse-tails. Fossil forests of 

 Calamites. Psaronius stems in situ and bearing roots at different 

 levels, suggesting growth in a region of rapid sedimentation. 

 Vertical stems either in loco natali or drifted. Climbing plants 

 possibly represented by Sphenophijllum, some species of ferns and. 

 MeduUosefe. Function of the so-called Aphlehia leaves of ferns. 



(3) Anatomical Evidence. 



The value of evidence afforded by anatomical features. Eisks of 

 comparison between structural character of extinct and recent plants. 

 Structure considered from the point of view of evolution, as the 

 result of adaptation to external conditions, and to mechanical and 

 physiological requirements. 



(o) Spores and leaves. — Abundance of spores provided with 

 filamentous or hooked appendages ; adaptation of spores to floating 

 or to wind-dispersal. The leaf structure of Calamites, ferns, etc. ; 

 presence of stomata, palissade tissue, and water - glands ; the 

 ' parichnos ' or aerating tissue in the leaves of Lepidodendrete and 

 Sigillarie^. 



QS) Stems and roots. — Absence of annual rings of growth. The 

 large size of water-conducting elements connected with rapid transport 

 (e.g. Sphenophyllnm) or with storage of water (e.g. Megaloxylon). 

 The chambered pith of Cordaites, quoted as evidence of rapid 

 elongation, of little or no physiological significance. Abundance- 



