20 BIOLOGICAL LECTURES. 



of a higher order than the possible identification of a new 

 species. The progress of botanical science in other directions, 

 however, notably in our knowledge of anatomy and a more crit- 

 ical appreciation of the significance which attaches to the devel- 

 opment of tissues and the growth of organs, has brought about 

 a radical change in the point of view from which we to-day 

 regard fossil plants. The very fact that we now apply to such 

 remains, so far as their nature admits, the same exact and 

 searching methods of study which are applied to living forms, 

 and that in them we recognize the possibility of discovering the 

 key to some of the most important problems in development 

 which confront us at the present time, imparts to this branch 

 of botanical work the same zest that is so marked a feature in 

 other departments of the science, while the many and often 

 great difficulties which surround the elucidation of any given 

 problem seem but to strengthen the energy and keenness with 

 which the pursuit is maintained. It is, therefore, a field which 

 offers abundant attractions to an enthusiastic and diligent stu- 

 dent; but for successful results it demands a broad foundation 

 in the science as a whole, and especially an intimate knowledge 

 of anatomy, both gross and minute. 



The difficulties which surround the study of fossil plants are 

 so unlike those to be met with in a study of existing species, 

 that a brief consideration of their nature and bearings may 

 serve to give a clearer conception of some of the facts which 

 I shall later bring forward. These difficulties may be grouped 

 under two principal heads : 



1. The nature and position of the material. 



2. The character of the alterations it has undergone. 



I. The Nature and Position of the Material. 



It seldom happens that fossil plants are found in situ. It is 

 quite true that, in the overlying slates of coal beds, ferns and 

 other characteristic plants are commonly met with, and are thus 

 to be observed in the places occupied during growth. We also 

 have similar examples in the erect Sigillarias of the South 

 Joggins, Nova Scotia, or the more recent submerged forests 



