243 
The third and by far the largest tribe is the Unoneae, in 
which the petals are also valvate, but they are equal or subequal 
in size or the inner may be much modified and smaller than the 
outer, sometimes being connivent and closely adpressed over the 
genitalia. I have had to be content with arranging the genera 
of this tribe into two subtribes, Xylopineae and Anonineae 
determined by the apocarpous and falsely syncarpous gynaecia 
respectively. Then the Xvylopineae resolve themselves into 
three series, the Hexapetalae, Tetrapetalae and T'ripetalae, accord- 
ing to the reduction in the number of the petals as indicated by 
their names. This arrangement, though undoubtedly rather 
artificial, reflects the comparatively rare tendency to reduction 
in the family, and will perhaps facilitate determination. 
No doubt the bad state of dried specimens has contributed 
much to the unsatisfactory classification of this family, explained 
by the fact that they are found mostly in dense moist tropical 
forests, wherein the collection of herbarium material presents 
more than ordinary difficulty, for the flowers, being mostly 
fleshy, shrivel when dry and become very brittle. 
Since the family was first monographed by Dunal in 1817, 
our knowledge has increased greatly through further exploration 
of the tropics. At that date only 103 species were known to 
botanists and most of these very imperfectly. In 1832, A. de 
Candolle’s review brought to light 204 species, whilst Bentham & 
Hooker’s estimate in 1862 was 400 species disposed through 40 
genera. The present work accounts for 95 genera and a moderate 
estimate of something like 1150 species.* The botanical explora- 
tion of Tropical Africa has brought to light a considerable number 
of new genera, especially the forest area from Nigeria to the 
Congo, and particularly the Cameroons, where many small 
endemic and peculiar types have been discovered. 
GEOGRAPHICAL DISTRIBUTION OF ANONACEAE. 
Anonaceae are almost wholly confined to the Tropics, where 
they generally grow at low elevations. For example they are 
very abundant in the rain-forest area of Western Africa, but 
nearly unrepresented in the adjacent and more elevated savannah 
regions. In Ceylon they do not ascend the mountains higher 
than 2000 metres, and in the Khasia Hills of Assam not beyond 
about 1600 metres. In Brazil their greatest elevation is probably 
about 1300 metres. The only genus extending for any distance 
into the temperate zone is Asimina, which occurs in Eastern 
America as far north as the Great Lakes. 
There is a marked contrast in the habit of the species of the 
two hemispheres. In the tropics of the Old World they are 
usually of climbing or straggling habit, and occur in dense forest 
areas; but in Tropical America they are nearly all shrubby or 
arboreal and mostly grow on the campos or open grassy plains. 
* The genus Hupomatia R. Br. is considered to be a distinct family 
and is not included. 
A2 
