4 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 
for the development of the pollen. The flowers are proterogynous, 
the stigmas maturing before the pollen sacs dehisce. 
The compound fruit, or syncarpium, is formed by the growing 
together of the carpels and torus into a fleshy mass, usually of an 
ovoid, spheroid, or cordiform shape, the individual carpels being 
indicated on the surface by areoles more or less distinctly outlined 
either with incised lines, as in Annona reticulata (fig. 25, p. 18), or 
by raised ridges, as in A. scleroderma (fig. 22, p. 17), and frequently 
bearing the produced tips of the ovaries, as in A. muricata, A. pur- 
purea, and A. cercocarpa. The areoles are sometimes swollen or 
gibbous, with or without a small wart or tubercle near their apex. 
Sometimes they are quite smooth or very faintly outlined, as in A. 
cascarilloides, A. glabra, and smooth varieties of A. cherimola. 
In most cases the fruit is greenish or yellowish when mature; in a 
few species it is glaucous or pruinose, as in A. sguamosa; or it may 
become suffused with red, especially on the sunny side, as in the 
bullock’s heart (A. reétculata). In the South American A. cornifolia 
and the closely allied A. nufans it is bright orange red. 
The seeds have the basal embryo and large ruminate or wrinkled 
endosperm which characterize all Annonaceae and there is usually a 
conspicuous swollen. caruncle around the hilum. In most species the 
testa is thin and membranous, revealing the wrinkles of the endo- 
sperm beneath, but in Annona longiflora and A. diversifolia it is 
thick, hard, and smooth, like the shell of a nut. 
GEOGRAPHICAL DISTRIBUTION. 
The genus Annona is confined almost exclusively to tropical and 
subtropical America. At an early date, however, certain species 
were introduced into the warmer regions of the Old World for the 
sake of their edible fruits, and were described as distinct. In addi- 
tion to these there are a few species endemic in tropical Africa. 
The latter belong apparently to three distinct groups, one of which, 
consisting of Annona klainii Pierre, in which there are sometimes 8 
petals and a 4-parted calyx, has been segregated as a section, Anonas- 
trum. Another, including A. senegalensis Pers. and A. stenophylla 
Engl. & Diels, has been placed in the same section with A. muricata L., 
but departs from that section in having the inner petals narrow and 
triquetrous, instead of broad and imbricate in aestivation. The third, 
consisting of A. glauca Schum. & Thonn., has both the outer and inner 
petals broadly ovate, and the coriaceous, subsessile leaves rounded 
at the apex and narrowed or cuneate at the base. As the present 
