PREFACE. Xlll 



To his botanical friends, A. H. Haworth, Esq. ; 

 Mr. Anderson, Curator of the Physic Garden, 

 Chelsea ; and to Mr. Don, Librarian of the Lin- 

 naean Society of London, he returns his best 

 thanks, for the readiness with which these gentle- 

 men severally answered every question proposed 

 to them on the subject. 



The figures, chiefly outlines, have been drawn 

 by E. D. Smith, F. L. S., from nature, in all 

 cases when necessary ; some of them are ideally 

 extended, but not without a close imitation of the 

 structure shown by the microscope. Superior 

 execution has not been aimed at, because an 

 accurate outline gives as perfect an idea as the 

 most finished drawings, especially of such parts 

 as are invisible to the naked eye ; neither have 

 these figures been too much multiplied, because 

 this would have been adding expense without 

 any real value. In fact the brevity intended did 

 not allow of much extraneous matter. 



