178 
ORIGINAL COMMUNICATIONS. 
Leaves simply and abruptly pinnate. Petioles often glandu- 
lous. Folioles opposite. 
Senna — Sepals of the calyx obtu se, anthers biporous, legumes 
membranaceous, broad, flat, compressed, many-celled, with 
transverse septa, hardly dehiscent, torous over the seed, 
scarcely pulpy within; seed vertical, parallel to, and com- 
pressed by the valves, nearly obcordate, shorter than the fu- 
niculus. 
In the shops there are two kinds of Senna — designated by 
the common appellations of Alexandrian and Indian. But with 
regard to the plants which afford these commercial articles 
respectively, considerable discrepancy and discordant state- 
ments are met with, attributable in a great measure to the diffi- 
culty of procuring and observing them in their natural state, 
and to the vague and indefinite language in which the most 
authoritative descriptions of them have been given, as likewise 
to the neglect of many minute circumstances, the observation 
of which would have tended to shed light upon those seem- 
ingly more important. Although from these causes the want 
of conclusive details renders many points doubtful, yet the 
nearest approximation to the truth can only be obtained by 
setting forth and contrasting the material facts asserted by 
different writers, so as to facilitate in correctly estimating the 
value which ought to be attached to them, and in establishing 
a sure basis for further additions to our knowledge. All sys- 
tematic authors who have treated of the different officinal 
Sennas, derive their statements from the accounts of travellers 
and botanists who have visited those countries in which they 
are produced, and therefore would seem entitled to confidence; 
the extent to which they are to be relied on will be seen in 
the sequel. But another method has been taken to obtain a 
knowledge of the several species of plants under considera- 
tion; it is by an examination of the article prepared and 
brought into the market for sale, and it will at once be per- 
ceived that this method is liable to numerous objections. 
Although in this way the species which are accurately known 
may be readily recognised, yet it is hardly warrantable to 
