A FULL treatment of the subject “Fossil plants as tests of climatic changes,” would require a more thorough acquaintance with fossil floras of various geological ages, as well as a wider knowledge of the distribution and conditions of life of recent plants, than I can lay claim to. Moreover the time at my disposal during the period allowed for the completion of the Essay was inadequate for a revision of the fossil floras, and a careful analysis of their geographical distribution. I have therefore confined myself to the endeavour to bring together such botanical and geological facts as seemed to me likely to prove helpful in climatal retrospects, calling especial attention to the several points of view from which previous writers have considered the subject. Various matters, bearing directly or indirectly upon the question, are briefly dealt with in the hope that such a summary may suggest methods for further enquiry, and facilitate the filling in of details in certain branches of the subject, the outlines of which I have roughly sketched.

I desire to express my hearty thanks to Professor T. McKenny Hughes and Professor W. C. Williamson for their advice and generous help, and also gratefully acknowledge suggestions received from Mr Carruthers and Mr F. Darwin.