Vlll PREFACE. 



Author, that, since the time he left the School in July, 

 1864, he has been but rarely able to revisit Harrow, and 

 then under such circumstances only as did not admit much, 

 if any, scope for Botanical research. His want of oppor- 

 tunity has, however, been more than counterbalanced by 

 the most valuable co-operation of the Editor. 



HONINGTON, SEPTEMBER 1, 1876. 



