PREFACE. 
As pointed out in the Preface to Section 2, the preparation of 
the preceding one, which is now completed, was delayed by 
unavoidable difficulties. It comprises two of the most important 
orders in the South African flora, the Hricacew and Asclepiadee, 
in both of which the specific characters require minute and 
therefore often lengthy description. The bulk of this Section 
has grown accordingly, and it is actually equivalent to that of 
two ordinary volumes. 
Dr. Harry Bo.us, who has given such munificent encourage- 
ment to Botany in South Africa, kindly undertook the elaboration 
of Hricacex, which for many years he had assiduously studied 
in the field. Professor Francis GuTuriz, LL.B., B.A., who 
had long collaborated with Dr. Bo.us, unhappily died on October 
19, 1899. The elaboration of the intricate genus Hrica is the 
result of their joint labours. The loss of his fellow-worker and 
his own indifferent health compelled Dr. BoLus to abandon 
reluctantly proceeding with the remaining genera. These were 
undertaken by Mr. N. E. Brown, A.L.S., who, in working them 
out, found it necessary to establish some new ones, and in other 
respects to depart from. the published key to the order. He 
has accordingly prepared a new one which will be found in 
the “ Additions and Corrections” at page 1123 of this Section. 
Mr. N. E. Brown has also worked out the Asclepiadex with 
immense pains. He has had the advantage of following 
Dr. R. SCHLECHTER, an acute botanist who has few rivals as 
a collector. Both have been disposed perhaps to cut their 
species rather fine. But South African botanists in the future 
will find less. difficulty in uniting species which cannot be 
sustained than in separating those which have been injudiciously 
united. Mr. Brown has himself been occupied with the study a a 
