8-10 mm. long, tube ca. 5 mm. long, lobes 8-5 mm. 
long, deltoid, subequal, entire calyx becoming necrotic 
following formation of an abscission layer at its base 
shortly after anthesis; bracteoles narrow, stellate-pubes- 
cent, gland-dotted, $—% cleft into 8-(4) lanceolate lobes, 
subtended by a nectary; capsules about twice as long as 
broad, glabrous, acuminately beaked, 3-4 locular, dotted 
with prominent darkly-pigmented glands, sutures form- 
ing partial, false septa at base and bearing a few long 
hairs above, ovules 4—6 per locule; seeds ca. twice as long 
as broad, covered with a single layer of brown fibers ca. 
6 mm. long; seed coat dark-brown, smooth. 
The affinities of G. Barbosanum are with the species 
of Section Anomala, which contains the botanically well- 
known G. anomalum Wawra and Peyr. and G. triphyl- 
lum Hochreutiner, as well as G. capitis-viridis, known 
only from the type specimen (which we have not seen). 
The major differences between the species of Section 
Anomala are indicated in Table I. Characteristics for 
G. capitis-viridis are taken from the type description, 
those for the other species from living material. 
One G. Barbosanum characteristic is worthy of special 
note since it distinguishes this species from all other spe- 
cies of Gossypium. Shortly after anthesis, an abscission 
layer forms at the base of the calyx, leading to its gradual 
and progressive necrosis; by the tenth day after anthesis 
the calyx is completely necrotic. 
The gametic chromosome number of G. Barbosanum 
is 18, the basic number of all the known diploid species 
of the genus. 
On the basis of comparative cytology (Beasley, 1942), 
each species of Gossypium is assigned to one of six ge- 
nome groups (A, B, C, D, E, or AD); G.anomalum and 
G.triphyllum have thus been assigned to the B genome 
group as B; and Ba, respectively. Preliminary cytologi- 
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