192 
CONTRIBUTIONS TO BOTANY. 
which is 1 -locular, with two opposite bipartite parietal placentge, 
each fork bearing a single ovule, as in ^giphila and Amerina. 
If these figures be correct, we must infer either that these spe- 
cies cannot belong to Ehretia^ or that the characters of the genus 
have been erroneously defined, and the tribe itsplf has been 
placed in a wrong family. These discrepancies show that we 
have yet much to learn in regard to the Ehretiece. If we hold 
Bourreria still in doubt, as well as Amerina^ for the reasons 
liefore given, there will remain only Ehretia itself to represent 
the tribe; and this offers so many anomalous characters that 
DeCandolle considered it must ultimately be divided into se- 
veral genera, of which he traced the outlines in Bourreria^ 
( 'armona, Xerodema^ and Menais. Xerodema has been shown 
to be identical with Rhahdia^ a Brazilian genus minutely and 
accurately described by Prof, von Martins in his ‘ Nova 
(xenera,’ and since figured by Sir Wm. Hooker (Icon. 823). 
'I’his construction, of a 1-locular ovary, with two opposite 
2-lamellar placentae bearing an ovule on each of their reflected 
margins, and a fruit with four nucules, each with a longitu- 
dinal open slit leading into two cells, is quite at variance with 
the structure that has been attributed to Ehretia and its allied 
genera. I wflll offer some observations upon Rhahdia and 
Cortesia under separate notices. 
The following is a synopsis of the genera of the Helio- 
tropieoe : — 
1. Fructus baccatus; albumen distinctum. 
A. Pyrenae 2, sing^ae 2-loculares. 
а. Embryo rectus; stamina inclusa; stylus brevis; 
stigma latum, breviter 2-lobuiii Toumefortia. 
B. Pyrenae 4, singulae 1-loculares. 
б. Embryo lunatim curvatus ; coroUae laciniae subu- 
latae ; stamina inclusa ; stylus longiusculus ; 
stigma majusculum, apice conico, piloso Messerschmidtia. 
2. Fructus exsuccus ; albumen distinctum, aut nullum. 
C. Pyrenae 2, singulae 2-loculares ; stamina inclusa. 
c. Stigma breve, vix divisum ; albumen nullum .... Hcliophytum. 
d. Stigma magnum, elongatum, profunde 2-fissum ; 
albumen distinctum Cochranea. 
r>. Pyrenae 2, singulae 2-loculares. 
e. Stamina longe exserta ; stylus tenuis ; stigma te- 
nuiter 2-fidum Tiquilia. 
E. Pyrenae 4, singulae 1-loculares. 
f. Antherae apice papiUoso cobaerentes ; stylus brews 
aut subnuUus ; stigma magnum ; flores interdum 
solitarii et axiUares Schleidenia. 
Antherae glabrae, oblongae, liberae ; stylus medio- 
cris; stigma magnum; flores in spicas longas 
curvatas terminales, 1-laterales Heliotropium. 
h. Antherae glabrae, globosae, liberae ; stylus simplex, 
2-fidus ; flores axiUares, solitarii Coldenta. 
