PREFACE. 
The two volumes of ‘ Illustrations/ published some years ago, were con- 
fined almost exclusively to the description of South American plants. 
Several reasons induced me to extend the range of these investigations ; 
and I now oflFer the first volume of ‘ Contributions to Botany,’ wherein 
the productions of both hemispheres are described. While engaged in 
examining the plants I had collected abroad, belonging to the family of 
the Olacacea, I was surprised to find in its two tribes great incongruity, 
not only in their normal structure, but in their subsequent development, — 
a difference of constant occurrence, whether the plants were of Asiatic, 
African, or American origin, bearing evidence that the two tribes are really 
distant in their affinities. This led me to extend the investigation further 
than was at first intended, and to complete a INIonograph of the whole of 
the second group, which I proposed should rank as a distinct order«(the 
Icacinacece), and which should take its place near the AqiiifoUacece. In 
pm-suing this investigation, I was aware of the responsibility incurred, 
and was conscious that nothing short of the most palpable evidence could 
avad ; for the IcacinecB had been associated with the Olacinea by one 
of the most distinguished and accm-ate botanists of our time, — an asso- 
ciation that had been accepted by all subsequent authors, and considered 
to be established. The investigation was therefore pursued with the 
utmost precision ; and the evidence thus collected will be seen to occupy 
the earlier portion of this volume. In support of the conclusions then 
inferred, the analytical details are now added in the accompanying plates. 
Nearly ten years have intervened since the text here reprinted appeared 
