PREFACE. 
It is now just a little over 50 years since Thomas Anderson published 
his (e Florula Adenensis ” describing 94 species. In 1905, K. Krause 
compiled a list of the plants reported from Aden in the past century, 
bringing the number of species up to 178. The catalogue of Aden plants 
which I wrote in 1907 mentions 196 species, and the present volume 
describes 250. Whilst revising and completing my former list by making 
use of the literature existing on the subject and examining the specimens 
preserved in various herbaria, I became aware of the great difficulties 
which lie in the way of identifying Arabian plants. This task requires 
not only a well-stocked library but also a considerable amount of leisure. 
Even then the endeavour is not an easy one, and would, in many cases, be 
unsuccessful, if good collections of African, Arabian, and Indian plants 
were not at one's disposal. Besides having in mind the scientific interest 
which attaches to the botanical knowledge of a country, it was chiefly 
with a view to facilitate the work of those who are interested in the 
vegetation of Aden, residents as well as travellers, that I decided to 
write this Flora. 
Most of the plants have been examined either on the spot or in herbaria, 
and where this was not possible, a note will explain on whose authority 
a species has been included. 
As to the description of orders, genera, and species, I made extensive 
use of the botanical works published on the neighbouring countries, not 
trying to change or add anything except in cases where good and well- 
preserved specimens gave a sufficient foundation for a more complete 
diagnosis. I did not wish to add to the confusion already existing in 
some publications. 
In order not to create wrong notions with regard to the flowering and 
fruiting season I considered it advisable to indicate not only the month but 
also the year. If the latter were omitted a great number of plants would 
be shown flowering regularly throughout the whole year, whereas, as a 
matter of fact, this is the case in a few instances only. 
Not too much reliance should be placed in the Arabic names. They were 
written down as they occur in various publications, spelt in the respective 
transcriptions of English, French and German botanists. Everybody 
knows what value may be ascribed to names taken down by travellers on 
the authority of some native guide who is anxious to oblige his employer. 
I am greatly indebted to Dr. A. R, Rendle of the Department of 
Botany of the British Museum, and to Dr. O. Stapf of the Royal Botanic 
